Note 1: Martin Griffiths (Maridvnvm on the Forum Classical Numismatics Discussion Board) has a die match to the obverse of this coin. He quotes Curtis Clay from a discussion about his coin in 2004 as follows: "That (obverse) die is under COS I in my cast collection. I read the wedge on bust as a I, but no second stroke under the bust.

There are some early COS I coins were the reading may be intentional, but yours is one of a smaller later group where COS I is apparently just an error, because by that time COS II was the standard and only correct title.

I have casts of two other coins from the same dies as yours, Oxford and Bickford-Smith coll., and two from the same obv. die with crossed cornucopias rev. type."

Note 2: This coin is listed on WildWinds under Septimius Severus, RIC 373v-3.