Edit: We have been told that “this is either a cut down/worn away Antoninianus or a barbarous copy commemorating Claudius II Gothicus after his death AD 270. The reverse is an Altar type ‘CONSECRATIO’, the IO is visible. It is close to the Garlanded Altar type RIC Vol V Part 1 Cladius II Gothicus No 261. There are barbarous types copying those made in a Roman Mint. It is a coin type we find quite commonly these days.”
“RIC = The Roman Imperial Coinage; Vol V = Volume 5. This RIC book volume was originally printed 1927 by Spink & Son ltd under Editors Harold Mattingly M.A. and Edward A Sydenham M.A and Part 1 is primarily the work of a Percy H Webb M.B.E. It was Reprinted in 1998 and 2001 by Bookcraft (Bath) Ltd. The actual book page designating RIC ‘CIIG’ Coin Number 261 is page 233 of the Vol 5 Pt 1″.
Thank you to Richard Ashford.