Hello, SMTS = Thessalonica. S (sacra) M (moneta) T (Thessalonica ??) (secunda??) Is the above breakdown correct for the SMTS marking? Thank you.
"TS" is the usual abbreviation for "Thessalonica" on tetrarchal coins after 294 in RIC VI. So, the "S" is not secunda, but part of "Thessalonica." When the mintmark in exergue begins "TS" the officina number may follow it, as in "TSA." However, when the mintmark in exergue begins "SM" as in "SMTS" the officina number is often in the right field, as in ........ Δ •SM•TS• (The CT software does not read blank spaces at the beginning of a new line, so I had to use "..." to move the delta to the right).
You may even change the font color of the "..." to white so as to make the dots invisible: ........ Δ •SM•TS•