Hi, The frame number shows up in the Bacon Twins & Triples book as a 1958 swinging-arm A-series frame. CoulD have been an A7 or A7'Shooting Star' (500cc) or an A10, either the 'Golden Flash', or the 'Super Rocket' (both 650cc) - these all used the 'FA7-' frame number prefix. The engine number would have been completely unrelated to the frame number. The numbering sequence starts from 101 - yours would be number 500 in the series. Can't see why it wouldn't be a genuine number - what would be the point in faking it? Records seem to show that it's in the correct place for that year: on the headstock. Any help?