Silver didrachm of Diadumenian (217-218), Tarsus, Cilicia, Roman Provincial coin

Silver didrachm (or drachm) of Diadumenian (217-218), Tarsus, Cilicia, Roman Provincial coinage M OΠ ANTOΩNINOC KAIC, bareheaded and draped bust right / TAPCOV MHTPOΠ, Nike walking left, holding wreath and palm. 21mm, 3.90 grams. SNG France 1556 corr. (obv. legend); BMC Lycaonia -; SNG Copenhagen -; SNG von Aulock -; cf. Roma Numismatics Auction 11 lot 526; cf. Nomos Web Auction 6, lot 663. Extremely rare, seems to be unpublished in most references, not sold in public auctions in the recent years. This denomination (known from two types) is sometimes referred to as a drachm and sometimes as a didrachm. It usually weighs around 4 grams and was probably intended to be equal to a newly introduced double denarius or antoninianus.