David Woods: Explaining the Cross: The Meaning of the Issue Marks used in Association with the Cross on Early Byzantine Gold Coinage.

Byzantine precious metal coins from the late 6th to early 8th centuries AD typically display a large cross on the reverse, with different styles of crosses for different denominations. Many issues also depict one or more letters in the field next to the cross, or sometimes at the end of the reverse inscription instead. The function of these letters is reasonably clear, that they serve to distinguish one issue from another. However, it is not at all clear what the significance of these individual letters is, why those letters in particular were chosen, or how they should be expanded, if they should be expanded. The natural temptation has been to interpret them as the abbreviation of mint-names, or as Greek numerals in reference to the indiction year or the regnal year, but these explanations do not work in most cases, since the same letters can be used repeatedly across several mints or several times during the same reign. It will be argued here that the best explanation for most of these letters is that they abbreviate some theological term used in description of the cross with which they are associated. Since theological terms (e.g. 'Theotokos') can sometimes be found used as issue marks on the copper coinage, most noticeably on the half-folles of Thessalonica during the reign of Justin II (565-78), it is arguable that the marks on the precious metal coinage represent the same phenomenon.