This coin appeared under thick encrustation in a batch my lad and I cleaned today... Posthumous half follis of Constantius I 2.1g 17mm RIC VII 206 OBV. DIVOCONSTANTIOOPTIMP REV. REQUIES OPT . MER (emperor seated holding short sceptre) PTR IN EX. 318AD
Thanks guys. ...... I took my time with it when I saw it was in a different league to most in the pile.