I see that it has a 16 tooth final drive sprocket, the smallest I have seen for a long, long time ! Perhaps it has come from a bike that was fitted with a sidecar ?
The ‘standard’ fitting was a 21T sprocket, and in the years when this type of speedo drive was fitted, the rear rim diameter would be 19″, (late Shipley and Brum). The vendor is Malcolm Leech, and I have bought all sorts of bits from him over many years, not just bike stuff, but vintage air guns, etc., etc..
Brian
