I think the one on my bike is a FG but it only says F.... I assume some of the stampings "missed" as the "0" of 60 is only half there too. Dating the frame it is a 61 bike, but the hubs etc would have come off a shelf and could have been older? I didn't realise that was rare, I thought all the Superbes had dyno hubs? I bet it's not as rare as the SW hub on my 1959 BSA Star rider!