Over on the Markup list (for discussion of text markup issues) we have been discussing the ligature of VI that appears in some Latin inscriptions. I asked:
We have come across several cases in the Inscriptions of Roman Tripolitania of the symbol that looks a little like an Arabic '4', but seems in fact to be a ligature of VI and stands for the numeral six (or, followed for example by II, part of a larger numeral VIII etc.) (1) is this a recognised symbol, and is there a Unicode codepoint that is either dedicated to it or acceptable to use to encode this symbol (as opposed to just for display)? (2) is there a common name for this symbol, better than "six-ligature" or "vi-ligature"?
(The symbol appears not to have a separate codepoint in Unicode, and nor should we expect it to be treated differently from U+2165, “Roman numeral six”, of which it is, after all, only a glyph variant. We have also, I think, answered the question of how to represent this symbol in EpiDoc [i.e. just like any other ligature].)
As an interesting aside, Paul Iversen suggested that there may some influence on this glyph-form from the Greek numeric stigma/digamma for six. There are plenty of other examples of the use of this symbol (including some useful Latin papyrological examples provided offlist by Rodney Ast). I include here the one photograph I have been able to find of a Tripolitanian example, where (VI)III = 9:
What do readers think? Is there any relationship between this and digamma? Is there a name for this ligature? Is there any argument for treating this any differently from a ligature of (NM) or (ΠΡ)?