I'm always on the watch for decent Carausius and Allectus coins. I only own one and two respectively. This coin may be rough, but it is identifiable so that makes it a good find. I think this attributes as:
RIC 165 Carausius AE Antoninianus 3.59 gr, 24.66 mm. London. 287-293 AD. IMP CARAVSIVS PF AVG, radiate and draped bust right / SALVS PVBLICA, Salus standing right, feeding serpent in arms. B-E across fields. Mintmark MLXX or MLXXI. RIC V-2, London 165