BSA Parts Catalogue for 1972 Twin Cylinder Models
Re-printed coil bound copy of the factory publication, A4 page size.
Covering Frame and Engine Numbers (at start of production year)
1972: A65 Thunderbolt: A65T-
A65 Lightning: A65L-
A70 Lightning: A70L-
In 1969 a new numbering system was introduced using a two letter prefix for the month and model season year.
The first letter designates months as follows:
A: January B: February C: March D: April E: May G: June H: July
J: August K: September N: October P: November X: December
The second letter is the year code:
G: August 1971 to July 1972 for bikes made for 1972 selling season.
Numbering started at 00101 and carried across all models.