It’s for a 41 bike Rik - so a lead acid would be correct I think - but I’m not bothered on this one really
It will be gutted & an electronic regulator put inside it
Job
John, It seems that they were marked "Lead-Acid" from September 1939 through until June 1942. I forget though that it's not really visible on the BSA. On Nortons, it's right out there.