Hi wade,
All BSA dispatch records are held by the UK BSA Owners Club and the information you require is available as a Dating Certificate that can be framed and sold with the bike.
Contact Steve Foden (Temporary Dating Officer) at 113 Holmville Road, Bebington, Wirral, CH63 2PX, United Kingdom.
There is a charge for this service of 5GBP for members and 10GBP for non-members and he will require pencil rubbings of the frame and engine number.
If you want to go down this route and have a problem with currency exchange, I can send him a UK cheque (check) in exchange for a PayPal transaction into my account.
Hope this helps.
Beezageezauk