Ro and the Coptic Numeral Hundreds

The alphabetic numeral system Coptic inherited from Greek works in three ranks of nine, and ro opens the third. The units run from alpha to theta with sou filling the sixth place, the tens from iota to the numeral sign for ninety, and the hundreds from ro to the numeral sign for nine hundred. That last rank needs the Greek derived letters through omega plus one further numeral sign, which is why the Greek alphabet in ordinary use, at twenty four letters, is three short of the twenty seven the system requires.

The seven letters Coptic added from Demotic have no place in the arrangement and carry no numeral value, because the values come with the Greek series and those letters were never part of it. Coptic scribes marked a letter used as a figure by drawing a line above it, so a reader met no ambiguity even in continuous script. Numbers appear constantly in Coptic books: quire signatures so a binder can assemble the gatherings, folio and page numbers, chapter and psalm divisions, and dates in the Coptic calendar. The colophon at the end of a manuscript, where a scribe recorded who copied the book and when and for whom, is often the single most useful line in a codex, and it is written substantially in letters used as figures. Ro at one hundred is where the largest of them start.