I've had this coin for a while and just don't know what to make of it. It appears to "possibly" be a legitimate issue as the legends are perfectly legible and design looks ok, although it is a bit rough, however the design and legend do not match. Size is 23.2mm and 3.1gms. Here it is (not the greatest pic): Obv: IMP CARAVSIVS P F AVG; Radiate bust right Rev: P(AX) AVG; Salus standing left holding rudder with left hand and feeding serpent coiled around patera with his right Obvious problem is that the reverse is not a PAX type, but is a SALVS AVGG type identical to one issued for Tetricus I ... but not for Carausius. What do you think, a barbarous issue or just a messed up reverse on an official type?
Gilbert Askew in The Coinage of Roman Britain lists, under 'Colchester', a variety with PAX AVG holding a 'wreath and baton, javelin or rudder' and gives RIC 329 as a further reference. I don't have time to investigate further right now, but maybe it's worth looking further into that and seeing what gets lumped in with that. For me, it looks early and/or barbarous, but the waters are muddy when it comes to Carausius.