CARAUSIUS. Romano-British Emperor, 286-293 AD. AR Denarius (18mm, 4.25 gm, 7h). London mint. Struck circa 287 AD. IMP CARAVSIVS P F AVG, laureate and draped bust right / F-E-LIC-ITA AVG, galley on waves, with central mast and four rowers, sailing right; RSR. RIC V 560; Shiel 47, pl. I, 47 (same dies); Casey pl. 2, 11. VF, darkly toned, slight obverse die shift, some flatness in centers.
Ex Richborough Castle Find.
This mintmark has yet to be positively identified, but see de la Bédoyère, "Carausius and the Marks RSR and I.N.P.C.D.A.," NC 1998, for an interpretation of RSR as a quote from Vergil's Eclogues iv.6-7: Redeunt Saturnia Regna, and the placement of the issue at London.