A set of 8 1962 to 1968 BSA Unit Twins Cylinder Base Nuts. 
Fits all BSA Unit Twins A50 and A65 (Lightning, Royal Star, Thunderbolt & Firebird Scrambler) for the years 1962 to 1968 only.
BSA part number equivalent: 24-5160.

For 1962-1963 shakeproof serrated washers were specified. I include a set of these too in case you want to use them. 
BSA equivalent number: 36-0382 (36-382).