Someone asked me about this coin, which they thought was a Constantinople issue. The obverse immediately struck me as a Thessalonica bust. This coin type is not known though. However, I am suspicious of this coin, as the reverse looks strange to me. Perhaps I am being overly cautious though...sometimes it is hard to evaluate a coin from a picture; but it does look like it could have been artificially aged. Perhaps it is just the lighting?
The second picture is a typical Thessalonica bust for comparison. The third picture is a star reverse issued from Thessalonica for Helena. The Helena type was issued 318- 319, while the reverse of this coin looks more like the A.D. 330 issue of star reverse types from Constantinople. However the obverse bust has a laurel headress, and by 328, Constantine was diademed. So if genuine, it would have been struck earlier than 330. See the last coin below for a Thessalonica coin from 330.
This coin is 16mm and 1.9gm, which seems like a half follis. Why the half- follis size, when the Helena and Fausta type is full size...lots of questions.
my email from 14 Feb about this coin--
"I would be cautious about this coin, it does not seem right. The obverse looks like something from the Thessalonica mint, like the coin I have attached. Helena and Fausta did have star in wreath types issued from Thessalonica. like the second picture attached. I would have to be sure of the background like provenance of this coin before I thought it was genuine."