Many of the
mint workers were illiterate - and were working very fast, so sometimes mistakes were made. The key is to identify true variants (recurring) versus minor variations (a mistake by one worker on a single die). I believe this is one of the issues with the
Class A2 table we've been using for ~100 years. It is a mix of major varieties and minor variations. I've been compiling data on
Class A2 (>3600 coins from
hoards, excavations, and major
collections) - and for some of these there are <5 known. I'd chalk that up to a minor variation, especially when the small populations are just a single dot/slash different than a major variety (say, >50 known) - and the
style of the coins is the same.
I'm glad you brought these variations in the IC XC to our attention. It's very interesting. We have no reason to believe that the
mint workers intended anything but IC and XC, given how prolific those letters are on the obverses of coins with Jesus on them. They made a lot of mistakes, for sure, and sometimes letters/words are missing. No reason to assume anything but mistakes on the
part of (likely) illiterate
mint workers working fast.
Regarding the meaning, the line above the letters indicates it is an abbreviation. IC XC is short for:
IC = abbreviation for IhSUS (Jesus). Sometimes IS is used for this abbreviation as well (as on the top of the
reverse of Classes B, D, E and F)
XC = abbreviation for XRISTUS (
Christ). Sometimes XS is used for this abbreviation as well (again, on the top of the
reverse of Classes B, D, E and F)
So, IC XC (with lines above) is the same
as IS XS (with lines above). Why they use these interchangeably - even on the obverse/reverse of the same coins? No idea.
On the pictures you shared, in one case the "E" is due to a double strike on the coin, not from the die itself: https://www.acsearch.info/image.html?id=3320742
There are quite a few XI coins, though, so that could be worth exploring.
Kevin