Hi Blackcat-I too am scratching my head identifying rear A10 mudguards.Your picture of the guard for sale looks to me to be the same pressing as the rear guard on my A10,(a more rounded profile with a small flare on the rear tip)- but i am convinced now that mine is an EARLY A65 job.There is one on E-bay now described as A65 lightning and its identical to mine. It is recessed on both sides at the front, obviously for the chainguard on the nearside, but also on the offside?, i believe A10 guards are not recessed on the offside. I wonder if some late A10`s had the more rounded type fitted as production of the A50/65 started, and BSA began to run out of the earlier mudguards??