Dropping the Base: Why Does Follis Production at Constantinople Appear to Cease for 24 Years between 842–866?

This article considers a period of Byzantine numismatic history where production at its main mint, in Constantinople, appears to cease altogether for at least 24 years, and arguably 26 or more years. It almost needs no stating that this is extraordinarily unusual in the numismatic record, and yet the topic has never been covered in more than a paragraph before. In this article, based upon my paper of the same title given to the International Congress of Byzantine Studies in Nicosia in January 2 020, I will explore the problem, setting it in its historical context and contrasting this cessation with others that scholars are aware of. I will argue that the pause in production was not accidental and can neither be explained in the context of the monetary contraction of the late seventh to early ninth centuries, nor by archaeological quirk. Rather, I will contend that this apparent cessation was a deliberate policy of the Empress Theodora and the regency council for Michael III , and that its subsequent continuation under the Caesar Bardas was perhaps more incidental, until the coronation of Basil brought the drive to restart production in Michael and Basil’s names.


Introduction
Coinage, and more particularly coinage from the mint of Constantinople, cannot really be said to be understudied, and therefore is not truly an 'untrodden path of Constantinople' . Yet there is a curious aspect of coin production at the imperial capital that has, to date, solicited no more than a paragraph in modern scholarship, and that aspect is the lack of any base metal coins reasonably identifiable to the mint of Constantinople between the years 842-66.1 By its very nature as a field that works with surviving archaeological material, the world of numismatics is replete with articles on newly discovered types and reappraisals of series of known and well-studied coins. Gaps in the record are much more difficult to write about and discuss than a physical object which can be observed, tested, measured and traced through find sites and hoard examples. To numismatists, gaps in production are annoyances to be explained away, and I will demonstrate and discuss some examples of this tendency below. But these gaps are usually a matter of months at most; 24 years, arguably even 26 years as will be considered below, is far too long to be a 'blip' , an accident of mint processing, or a quirk of the archaeological record and nature of the market for private collections.
The methodological theory in numismatics is that mints, and especially the primary mint, must continuously be producing coinage, and base metal coins in particular, to service the needs of the economy. There are plenty of good rationales for a state to continuously produce coinage more broadly. The first is to maintain the flow of coinage to the economy to compensate natural loss, which is the accidental loss of coin; the deliberate hoarding of coin so that it does not circulate freely within the economy; or the repurposing of coinage as jewellery, bullion or other purposes (though this tends to affect the gold and silver coins more than the base metal). Second is the propaganda value of coins -here it is often theorised that the base metal is the most precious in terms of propaganda value, since it circulated the most widely, but it is very often the gold or silver which is altered for ostensibly propagandistic purposes, while the base metal alterations are more a reflection of practical concerns. 1 I use the term 'base metal' in preference to the 'bronze' more commonly found in Englishlanguage publications or 'copper' more commonly favoured in other European language articles. This is because while these coins almost certainly always contain copper, they almost certainly always contain more than just copper, but there is no dedicated metallurgic study into their composition. The field of Roman numismatics has, for these same reasons, shifted towards the term 'copper-alloy' , but in preferencing 'base metal' I am following the precedent set down in Hendy, Michael, Studies in the Byzantine Monetary Economy, c. 300-1450(Cambridge: Cambridge University Press, 1985.
Third, while the concern of the imperial government for the wider Byzantine economy could be debated, coinage was an important arm of the state in terms of the payment of its officials, and it would therefore be desirable to continuously produce coin. Despite this theoretical framework, there are periods of demonstrable gaps in production visible through the numismatic record. My baseline assumptions in writing this paper are not that the theoretical framework of the administrative necessity of coinage is correct, and that the attributions and understanding of the extant body of coinage should be explained in light of this framework. Rather, my underlying assumptions are that the attributions of the extant body of coinage are broadly correct, and that the theoretical administrative framework ought to be reconsidered in light of the extant body of coinage, including this gap in the record which has been almost systematically ignored to date. I take this position precisely because the perceived sanctity of the theoretical framework is likely in part responsible for the academic ignorance of this period of non-production.

Bibliographic Review
First of all, it seems a useful exercise to outline the historiography of the problem, such as it exists. In 1858, Justin Sabatier did not mention the lack of Constantinopolitan folles for Michael at all.2 In 1908 Warwick Wroth mentioned the problem only in a footnote: 'The absence of bronze of Michael III (alone) is noticeable, but probably the bronze of his father Theophilus (at the present day extant in considerable numbers) continued to supply the currency.'3 Despite working largely from Wroth, Ivan Tolstoj ignored the issue entirely in 1912-14.4 In 1970, Cécile Morrisson did mention the problem very briefly in the main text: 'Il n'y a pas de folles frappés pendant le règne de Michel III seul' with the footnoted explanation: 'Probablement parce que les émissions abondantes de Théophile suffisaient aux besoins de la circulation.'5 This was the first time the problem was recognised in the main text of an academic work, albeit brief. later in 1973, Philip Grierson tackled the issue in slightly more depth.6 In summary, Grierson acknowledged the problem, outlined how we numismatists usually dismiss gaps in the record, explained why this cannot apply to a gap 'that lasted for a quarter of a century' , and then provides two possible explanations for the problem, one of which is an uncited reiteration of Wroth and Morrisson's footnotes.7 Grierson is convinced by neither of the solutions he presents: either that there were so many Theophilan folles that there was no need to produce more, or that there was the continued striking of folles posthumously in the name of Theophilos. 'Both' he notes 'would have been contrary to precedent, and it is impossible, on the evidence at present available, to decide between them.'8 In the same year that Grierson published volume III.1 of the Dumbarton Oaks catalogues, Philip Whitting noted in his Byzantine Coins 'the only copper folles from the capital come in 866-7 with Michael on the obverse and Basil I on the reverse.'9 There was no attempt to explain this, or even note how odd such an occurrence was. Philip Grierson's next potential contribution in a similar format to Whitting's was his Byzantine Coins in 1984, but it remained entirely silent on the issue. One year later, Hendy's Studies in the Byzantine Monetary Economy utterly ignored the issue, choosing to focus instead on Michael's supposed plan to melt down church wares for coin related by a propagandist for Constantine VII and thereby Michael's murderer, Basil I.10 This is a surprising omission for a book concerned with the monetary economy -if the principal mint of the empire was failing to produce the principle unit of exchange, surely this must be of more significance to the Byzantine monetary economy than a spurious story about the melting down of church wares which, even by that story's own admission, never came to pass anyway. Most recently, in 2015, Morrisson has suggested that Grierson already 'resolved' the problem with his 'ingenious solution' to the question of the use of the terms imperator and rex on the folles of Michael and Basil, which presents the letters from Pope Nicholas I as the rationale for restarting mint production.11 Not only is this a solution not explicitly written by Grierson for the problem of why striking restarted at Constantinople, but Morrisson also asserts that Grierson explains the apparent pause in production as being due to the voluminous issues of Theophilos and the pause filling a 'circulation requirement' . As noted above, Grierson did not state this with any semblance of certainty, this was rather what Morrisson herself had already written 45 years earlier.
What this bibliographical review provides is the rationale for the present article. I do not propose to provide any further evidence to support either of Morrisson and Grierson's solutions, nor will I propose an alternative solution. Rather I intend to illuminate the (almost entirely) 'untrodden path' of the problem of Michael III's non-existant folles which has been made dark by over a century of silence, brief acknowledgements and outright dismissal of the problem as 'solved' . This issue is a numismatic anomaly, but an ignored anomaly allows academically acknowledged orthodoxies to go unchallenged. As Ted Buttrey once sagely noted on a separate numismatic issue: 'It is the consensus that is the problem: scholar B accepts the routine followed by scholar A, and scholars C, D and E join the bandwagon, and in support they cite each other. Agreement and repetition have conferred a spurious authority on an operation which did not work in the first place.'12 In this specific instance we are observing the opposite effect -an unintentional conspiracy of silence and near-silence is bolstered by suggestions that the problem has been solved, "please move on there is nothing to see here", has meant that a serious academic question pertinent not only to historians of the reign of Michael III, but to Byzantine numismatists more broadly, has remained virtually unseen.13

Gaps in the Record
As an additional backdrop to the problem that is the focus of this article, it seems additionally useful to consider other examples of gaps in the numismatic record, which are chronologically comparable. In the century preceding the gap under scrutiny in this article, there are observable gaps for the production of coinage at any mint for the five and a half months between the death of Constantine V/ accession of Leo IV in October 775 and the coronation of Constantine VI as Leo's co-emperor in April 776; for the reign of the Emperor Constantine VI (780-97) at the mint of Syracuse specifically before it re-emerges under Eirene's sole rule; and for the two months of Staurakios' sole reign in 811 at all mints. These are often dismissed as short gaps with rational explanations. For the period of the two-month nominal reign of Staurakios following the death of Nikephoros I in 811, the emperor was on his deathbed, and producing new coins in the emperor's name can hardly have been a pressing concern, since his very survival was not certain.14 As a very short period of time, it is also sometimes explained as a dearth of archaeological material, in the same way that dated series of coins may be missing any examples of a particular year, or particular officina mark, though this explanation is increasingly unlikely with the passage of time, albeit technically possible and therefore worth acknowledging.15 The gap for Leo IV can be explained politically -that he was waiting for the coronation of his son, or that the power behind the decisions about coinage had either passed out of government with Constantine V, or was Constantine V himself.16 Again, this gap represents a matter of months, not decades. For other mints, the explanations may best be sought in their own local histories, rather than imperial directives. For the Constantinopolitan mint, for over 24 years, such explanations are woefully inadequate.
While it is not possible to assess the continuity of annual production after the beginning of the eighth century, when the regnal year dating disappeared from the base metal coins, coin production at the capital does continue even It is worth noting that the issue of a dearth of archaeological material is not uncontroversial. There is often now a sense among numismatists that all types should be known to us by now, and it will no longer suffice to say that a gap may be explained by a paucity of archaeological material. In the broad aspect, I agree, it is an insufficient explanation alone. It is not, however, impossible, and ought therefore to be acknowledged as potential, if unlikely. It is still possible for significant new types to come forward. See for example Vrij, Maria, "A new coin type from the mid-seventh century?" in Goodwin, Tony  through the period of monetary contraction. No emperor lacks coinage entirely, excepting Staurakios, and the dearth of material can be explained by the pattern of usage of the coinage, and of the change in settlement patterns and where can be systematically excavated.17 In any period, a gap of at least 24 years cannot be explained by the above explanations for other, much shorter, gaps in coin production. For the period between the reforms of Michael II and of Theophilos and the period of the Macedonian increase in coinage, it appears especially strange. The period 820-912 appears as one of monetary recovery, to have over two decades of that time with absolutely zero base metal coins produced at the capital mint is more than a little peculiar. The period of monetary contraction represents fewer coins found; it does not necessarily represent fewer coins produced, though it is highly likely that fewer coins were indeed produced; but, importantly, it represents a dearth of coins, not a total absence of coins. The period 842-866 represents no base metal coin production at the capital mint at all, unless it was producing coins posthumously in the name of Theophilos. Since the capital produced both gold and silver coin, this cessation has to have been part of a deliberate policy.

Attributions
If not a cessation of coin production, there are two further avenues which need exploring: that the reformed follis of Theophilos continued to be struck posthumously during Michael's reign; or that folles of Michael's reign have been found, but misattributed elsewhere. This section will briefly consider the latter possibility.
For coinage with the name Michael, the "ambiguous Michael coinage" is pre-c.821 reform, and so is probably correctly assigned. For the coinage with two figures: Michael and Theoph' , the Theoph' is either Theophylaktos, the son of Michael I or Theophilos, the son of Michael II, hence the adjective "ambiguous", and Michael III was not known to have had a co-emperor by a name beginning Theoph' .18 The coinage of this group of Michael alone is not only pre-reform in style, but also known as an undertype to certainly pre-Michael III coinage, making it certainly earlier. The Michael coinage assigned to Syracuse for Michael III is a surprising return to a pre-Theophilan reform type, but in size and style it is much more closely related to Syracusan coinage before and after. For Michaels IV, V and VI, their reigns are during the period of the anonymous folles, and by Michaels VII and VIII, the style of the coinage is so very far removed from that of the early ninth century, that these cannot be misassigned, and such a conclusion is supported by the evidence of overstriking.19 It is also improbable that any coins of the anonymous follis series could belong to the reign of Michael III.

The Reforms of Theophilos
In order to consider the gap, it is easiest to define, briefly, the coinages which do appear either side of that gap. From around the reign of Constantine IV (668-85) base metal coinage becomes a decreasingly commonplace find at archaeological sites and through single finds as represented in museum collections and auction sales. This dearth continued -particularly in Anatolia and the Balkans, but less so in Sicily and Southern Italy -until the coinage of Michael II and Theophilos (821-9), when finds start to increase once more, though the end of the period of monetary contraction is usually pegged around the coinage of Leo VI (886-912). The reform of the follis by Theophilos is an important part of the picture of that increase in coin finds.20 It is not possible to date the reforms with precision. There are two broadly identifiable Constantinopolitan pre-reform types with the M denomination mark. The first with Theophilos alone (see Fig. 1) the second with Theophilos and his first son, Constantine (see Fig. 2). Since dating Constantine's birth, co-emperorship and death is problematic, this makes dating the reform the reign of Theophilos, whereas a larger number of short die chains might be more suggestive of a large number of mints operating simultaneously.26 There are not commonly overstrikes of this series, so suggesting simultaneous or sequential production is not easily provable via this method. If it were possible to pursue, however, it might indicate more clearly whether the Theophilan reformed folles represented a mass-produced coin across the Empire (perhaps prefiguring what may be the case with the later Anonymous Follis series), or a series produced during this apparent 24-year gap posthumously in Theophilos's name.27 It is worth additionally noting at this point why the gap in production may be even longer than 24 years. While there are solidi and miliaresia (see Fig. 4) in the name of Theophilos and Michael (i.e. gold and silver coin directly attributable to the years 840-2), there are no equivalent folles. For the presently undatable period of the co-emperorship of Constantine, the late elder brother of Michael, there are coins of all three metals. It may be that the decision to cease follis production at Constantinople was not taken by the regency council for Michael in 842, but by Theophilos himself in or before 840. While this is a possibility that should be noted, it does seem more plausible that the choice was to continue the new reformed follis as it was because of its peculiar propaganda value.

The Other Coinage of Michael III
It is worth noting here that coin production does not cease altogether between 842 and 866. There are gold and silver coins of Constantinople, and coins believed to be from the mints of Syracuse and Cherson. In gold, Syracuse continued much as it had for the past century, but with the debasement of its gold coin now often visible to the naked eye.28 In base metal it reverted to a version of the pre-reform type, with the denomination mark M (see Fig. 5 720. It is worth understanding this within the context that Syracuse as a mint had been exhibiting an increase in autonomy from Constantinopolitan models since around 690, which seems to have stepped up during the reign of .29 This disconnect to the capital is further observable through other lines of investigation.30 It is therefore entirely plausible that if there was a centralised decision to cease follis production under the regency for Michael III, then the mint of Syracuse was not following it. Similarly to Syracuse, the mint of Cherson was following its own path, which can be understood independently of actions at Constantinople, though it is clearly more connected to the capital at this period of time specifically. In brief: Cherson had been only arguably part of the Byzantine Empire through the eighth century. By scholarly consensus, its final imperial coins prior to Michael III had been struck in the name of Constans II (641-68), whereafter its coins were cast in the name of the city or the prōteuōn, or prōtopolitēs, 29 Vrij, Byzantine Empire and to its northern and western neighbours, the coin output of Cherson is also better understood in its own local context, separate from the situation at Constantinople. To return to Constantinople, there are gold and silver types representing almost every stage in Michael's emperorship. For gold there is the type with Theodora, Michael's mother, Thekla, Michael's eldest sister and an augusta herself, and then the child Michael himself, usually dated between 842 and 843. Then there is the type with Theodora and Michael and Christ, usually dated from the council of 843 until the end of the regency of Theodora in 856. Then the type with Michael alone with Christ, usually dated to the period of Bardas's Caesarship through Basil's co-emperorship to Michael's death (856-67). Curiously, there are no known gold coins for Michael and Basil from Constantinople, even though there are base metal coins for both (see below). This pattern is similarly imitated in the silver. A type with Theodora, Thekla and Michael, then two types of Michael alone, one with the standard old cross design and the precedented inscription + mIXA/HL EC ΘEЧ / PISTOS bA/ SILEЧS RO/mAIOn (Michaēl ek theou pistos basileus rhōmaiōn), the other with a modified cross that would appear on the Makedonian miliaresia and the new inscription + mIXA/HL PISTOS / mEʕAS bA/SILEЧS RO/mAIOn Basileus is my own suggested additional interpretation: Vrij, Numismatic Iconography: p. 110. (Michaēl pistos megas basileus rhōmaiōn). As with the gold issues from the capital, there are no coins of the joint reign of Michael and Basil, though it is worth noting that there are gold issues for Michael and Basil from Syracuse -its mint again acting independently from the capital here.
From the base metal perspective, there is a follis type belonging to the joint reign of Michael and Basil; however, its source mint is the subject of scholarly debate. This type is shown in Fig. 6, and displays a bust of Michael on the obverse and Basil on the reverse. Both wear the loros and a cross crown and hold a globus cruciger with a patriarchal cross in their right hands. The part which usually excites the most attention, however, is the inscription. Rather than the historic basileus and despotēs for the emperor and his co-emperor, or the even more historic augusti, this coin designates Michael as imperat [or] and Basil as rex. Originally, these coins were considered to be of a 'provincial mint' .37 Wroth later reassigned them to Constantinople and most scholars since have followed suit with varying degrees of justification.38 Grierson explained the Latin language inscriptions (this includes the spelling of Michael's name, which uses a CH instead of a Greek X) as connected to a dispute with Pope Nicholas I, of which only one side of the correspondence has survived, where the Pope questioned how Michael could call himself Emperor of the Romans when he could not even speak the Roman tongue.39 This interpretation has been broadly accepted, though more recently Rovelli has reconsidered this series as belonging to the mint of Naples.40 I do not find any of the arguments wholly convincing, but which mint these coins are assigned to has enormous implications for the apparent dearth of base metal coinage from Constantinople that precedes it. 37 Sabatier, Grierson's argument, followed by Morrisson, is that the coins are artistically 'Eastern' , and should therefore be attributed to Constantinople, and that the dispute with Pope Nicholas gave an impetus to produce this series of coins with the Latin.41 Grierson himself notes that the lettering is not consistently 'Eastern' , and while coins of this type are stylistically quite divergent from the Neapolitan issues for Sergius (840-67), they are also not wholly similar to the presumed Constantinopolitan coinage of Theophilos before, or Basil I afterwards. Moreover, while Grierson's argument in relation to the letters of Pope Nicholas is, as Morrisson puts it, 'ingenious' , it fails to explain why this should appear on the base metal coinage, and not the gold, which might have been sent to Nicholas as a pointed gift, rather than use a material that was more associated with localised monetary exchange. Additionally, the capital mint had a much stronger production line for gold than for base, if we consider this period to represent a gap in striking, rather than of posthumous Theophilan issues. Rovelli's argument, which appears only as a long footnote in an article more concerned with Lombard coinage, accepts Grierson's point on the artistry, 41 Grierson but believes the spelling of the name of Michael with the Latin CH makes an Italian, and probably Neapolitan, origin more likely. Her explanation for why the reemergence of Byzantine imperial coinage at Naples at that point is the hellenism in the city, however, why then produce a coin in Latin, when Greek, or at least Greek dialect, was linguistically more commonplace? Her point that the loros is worn by both emperors when it would be more regular to see either a double chlamys, or a chlamys and a loros, is worth further consideration. For the mint of Constantinople, this is certainly true, but the mint of Syracuse had for over a century shown a divergence from this model with no discernible pattern to the usage of the imperial costume. While it is worthy of note, and a caution against assigning to Constantinople, it should also be noted that the mint of Constantinople had for 24 years either only produced figural gold coinage (the silver displaying only a cross and inscription) where Michael wore the chlamys, or had continually produced base metal coinage only in the name of a single emperor, Theophilos, who wore a loros. It is also worth noting that base metal coins attributed to Constantinople during the reign of Michael's successor, Basil I (867-86), depict basil alone in the loros, Basil and his son Constantine both in the chlamys, then Basil, Constantine, and Leo with Basil in the loros and his sons in the chlamys; perhaps this type of Michael and Basil sets that trend, even though Basil's base metal coinage abandons the model set by his coinage with Michael III in favour of something more typographically similar to Theophilos's reformed coinage.
To these points on this coinage I should like to add the following observations. Regarding the titulature, it is not only significant that they are in Latin, but that the titles are imperator and rex, not Augustus, Caesar, or dominus. The latter of the alternative titles is a simple translation of the commonly used despotēs for the junior emperor, Basil in this instance, which also had more recent precedence on the coinage in the abbreviation DN for dominus noster/ domini nostri, than imperator had.42 Caesar, however, is numismatically about as historical as imperator, but it also had connotations to the German Holy Roman emperors, who called themselves Kaisar, and to a Byzantine imperial title which was below the rank that Basil held and notably a title held by Basil's deposed predecessor, the Caesar Bardas. Augustus, on the other hand, had a recent and identical usage in Greek as demonstrated by Theophilos's Greek 42 DN had last been used on the coinage of Constantine V (741-75), unless Anokhin's dating of the unusual Chersonese type discussed above to Theophilos is accepted. It is worth noting that the presence of DN on that type is part of my rationale for a dating earlier than Theophilos, but in any situation, that type is so unusual as to be implausible as an example setter. Imperator had disappeared with the reforms of Anastasius I (498). language reformed follis: Theophile auguste su nikas. If the rationale for the coin type was the exchange with the Pope, then the use of imperator would make clearer the ability to use Latin than the use of augustus, in the same way that a student of French as a foreign language may choose the more specifically French word 'gendarmerie' over the more pan-European 'police' in order to demonstrate their command of the language. The particular choice of titles would seem to support Grierson's view that this follis type was imperially chosen as a response to the dispute with the Pope, though why this appeared on base metal, and not gold remains unclear. To follow Rovelli's argument, one has to wonder why imperator and rex were chosen over the arguably more natural augustus and dominus; the non-use of Caesar being explicable again by the titulature of the neighbouring Holy Roman Empire. It is for these reasons that Constantinople still seems to be the best guess for the mint place of this series, though it is with great doubt that this conclusion is reached, or rather, reasserted.
For the primary concern of the present article, this means that either the recommencing of follis production at Constantinople began, or the end of the posthumous Theophilan coinage occurred in 866 with a deliberate imperial decision, just as it had ceased through deliberate imperial position. Tangentially, it also has implications for a deliberate decision to not include Basil on the gold or silver coinage at Constantinople.

The Politics of Michael's Reign
Since the cessation of follis production or continuation of posthumous Theophilan coinage must have been a deliberate policy, it is worth briefly considering the politics of the reign of Michael III. For the first fourteen years of his reign, Michael was under the regency of his mother, Theodora, and a regency council. It was they that convened a small assembly in the palace to repeal imperial iconoclasm for the final time in 843, and probably had gold coins struck commemorating this.43 Part of Theodora's motivation at this council appears to have been the maintenance of a good name for her late husband Theophilos, and thereby the good name and reputation of her children, primarily Michael, the nominal emperor, but also her daughter Thekla, who may have been groomed as a successor should Michael die in infancy as Constantine had, and her other living daughters.44 In this context, the motivation for a posthumous coinage seems apparent, but it is not mirrored in the gold or silver coinage of the capital, which might otherwise be expected. Moreover, this picture of the coinage from the capital continues during the caesarship of Bardas, Michael's uncle. Bardas ousted Theodora and the remaining regency council in 856, nominally in favour of the now adult Michael, but became only Caesar, not Augustus and co-emperor. Theodora is likely removed from the coinage at this point. That Bardas does not appear should not be a surprise, since Caesars tended not to appear on coinage -witness here Alexios Mousele, who did not appear on the coinage of Theophilos, or earlier, Heraklonas, who did appear on the coinage of Herakleios as Caesar, but did so uncrowned.45 In any eventuality, there is still either no Constantinopolitan base metal coinage for this period or the continuation of a posthumous Theophilan coinage. Given the removal of Theodora from the coinage, either continuation, or a move from posthumous Theophilan coinage to no folles, must have been a deliberate decision from the new governmental configuration. It is difficult to imagine a motivation for Bardas to continue the coinage of Theophilos, but Michael was by this stage an adult, and he may have wished such a series to continue.

Conclusions
In summary, it seems almost impossible to find a solution to the question "did follis production at Constantinople cease for over two decades, or were there over two decades of folles struck posthumously in the name of Theophilos?". It may be possible to suggest an answer through a full die chain study of the Theophilan reformed folles. Whichever answer may be arrived at would be entirely unparalleled in Byzantine numismatic history, and so scholarly debate as to the reasons why this occurred will likely never reach a conclusion. It is simply not within the realms of realistic possibility that folles which fill this gap will be turned up in the future, nor can the phenomenon be adequately explained as related to the period of monetary contraction. It seems equally implausible that the coins have been found but misidentified.
The decision to either cease follis production or continue Theophilan follis production posthumously can only have been a deliberate decision by first the regency council for Michael, then by Michael and the Caesar Bardas, and these may in turn follow on from a deliberate decision by Theophilos, whose mints produced no base metal coinage in the name of Theophilos and Michael III. It is precisely because this phenomenon was the result of at least two separate deliberate governmental decisions that this period and its peculiar coin production pattern at the capital should be studied, acknowledged and discussed more widely. This period may be the exception that proves the rule of Byzantine monetary policy (if such existed in any deliberate or consistent way), but this should not mean that it is ignored and omitted from the story of the Byzantine monetary economy, as it challenges many of our assumptions about the necessary nature of coinage, even during challenging times for the monetary economy such as the late seventh to early ninth centuries. For the more general historian of the Byzantine Empire in the early ninth century, it also fleshes out the picture of the reign of Michael III and the actions of the various potentates at his court. Though the economic impact of this decision has been outside of the boundaries for this paper, it is its own important question, worthy of further consideration in another place.
It is perhaps because of its apparent unresolvability that the problem of follis production at Constantinople in this period has been so poorly studied in the past. Because of its unparalleled nature, however, it is very important that it is studied and discussed. The historic passing over of this topic has contributed to a general ignorance of a very significant period in Byzantine numismatic and economic history. The very nature of academia has become such that unresolvable problems go ignored, and become almost imperceptible to our colleagues and to history itself. It is therefore important that, where possible, these unbeaten paths of history are trodden and tended, so that they might form a part of the more general map of the past. While I have not been able to provide any concrete solutions to the question of why follis production appears to have stopped at Constantinople for at least 24 years between 842 and 866, I hope this article has contributed to some preliminary weeding of this overgrown unbeaten path of Constantinople.