Wow, you guys are good! Many thanks, jskirwin, Biancasdad, and FVRIVS RVFVS, for your help! Great attribution, for a coin that's difficult to read.
I looked up the KA that is found in exergue and find that on the website given above it is listed as the mintmark for coins from Serdica, Tripolis, and Cyzicus (seems unlikely to me to be correct for all of these). I also read elsewhere that because this is before the monetary reform of Diocletian, KA could be a Greek translation of XXI, indicating the number of base denarii this coin is worth.
Edited by Seeker55
03/06/2018 7:39 pm