It appears to be an antoninianus of Emperor Trajan Decius. Nice portrait too. Looks like Victory on the reverse. I have a coin of his, though of a different reverse to yours. Trajan Decius, AD 249-251 AR Antoninianus, 22mm, 4.2g, 12h; Rome mint. Obv.: IMP C M Q TRAIANVS DECIVS AVG Radiate, draped, cuirassed bust right. Rev. DACIA Dacia, wearing long robes, standing left, holding vertical staff with ass’s head. Reference: RIC IVc 12b, p. 121
There are several bust styles for Decius. This is not the most common one. I don't know enough about it to doubt the coin. Below is the closest I have.