The S497 is the important bit. I think the other two variables refer to the bezel type and the length of the trip meter cable. Incidentally, the flex speed for Ariel chronometrics is 1610. Ariel PA speedos run at 2240.
36 4G, 37 VH, 53 ex ISDT KHA (project), 54 KH(A), 54 4G Mk IV (project), Healey 1000/4 (project)
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser.