As I understand it, at some point in 1970, BSA started putting the model designation (A65L, A65T) on the engine as the suffix while maintaining it as the prefix on the frame. The date code, however, stayed in front of the serial number.

A smattering:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.