Roman Provincial Needing ID

Reverse probably reads ΟΥΛΠΙΑΝΩΝ ΑΓΧΙΑΛΕΩΝ. Anchialus, Trace.

Obverse is, perhaps, Caracalla, similar to (if link works):
https://www.wildwinds.com/coins/ric...chin_157.jpg
and
https://www.coinarchives.com/e6c092...age00802.jpg

Reverse is more like this Septimius:
https://www.forumancientcoins.com/g...?pos=-105886
and
https://cNGCoins.com/Coin.aspx?CoinID=152697

I've seen printed descriptions of the Anchialus Caracalla obverse with the reverse of serpent and ΟΥΛΠΙΑΝΩΝ ΑΓΧΙΑΛΕΩΝ. But I've not seen a pic of this type.

I could certainly be wrong, but I don't think you'll find an example. I think it's probably quite rare. (Don't assume that makes it valuable, though)

It is likely from Anchialus, Thrace. The obverse is, I believe, similar to the AE26 in the Wildwinds link above (Lischin 157). The reverse is similar to the Septimius Severus reverses I linked to, which come from similarly sized coins.

There is a reference, sadly unillustrated I believe, in the Numismatic Chronicle Vol. III (1841 - available through Google Books online), page 107, to an "unedited" (I take that to mean unpublished) Caracalla bronze from Anchialus that may refer to this variety. It lists an AY K M AY ANTΩNINOC obverse, with "Laureated head of Caracalla (wearing) paludamentum to the right." The reverse is described as "Serpent coiled up, his head erect" and with the ΟΥΛΠΙΑΝΩΝ ΑΓΧΙΑΛΕΩΝ legend. The author, H. P. Borrell, writes, "There is nothing particular in (the coin) except (that it is) unedited." Although the size is described as "AE 6 ½" I don't know what that meant back in the early 1800's, as opposed to the AE scale today. My assumption is that it's in the range of the other AE's we've been discussing.

If the Chronicle listing refers to the same variety of the OP coin, I wonder whether the coin was a very limited minting or perhaps a mule of some sort. You may need to find yourself an expert on Thrace Provincials!