Puzzled by the engine number on a BSA 500? I was offered yesterday. The stamping of the 'GS' looks weird and I've never seen a factory stamp font like that. I'm wondering if the vendor is trying to fake the 'Gold Star' numbering? Any help would be gratefully received. Thanks
Clearly a ZB31 stamping which has been subject to rather naive tampering with by adding the G and S either side of the original full stop.
There was never a ZB31GS. If it was a Gold Star it would be marked ZB32 GS xxxx. There was also an iron engined B32 (I have a ZB32) and and alloy B32A, which gets confused with the Gold Star.