My guess is a provincial bronze from Viminacium. Here is one of Trajan Decius (not mine) with a similar style and weight. Trajan Decius Æ25 of Viminacium, Moesia Superior. Dated Year 12 = AD 250/1. IMP TRAIANVS DECIVS AVG, laureate and cuirassed bust right, seen from behind / P M S COL VIM, Moesia standing facing between bull and lion; AN XII in exergue. RPC IX online 23; Varbanov 166; AMNG I 128. 11.31g, 25mm, 6h.