"suddenly the whole combination pops into my head. 1626. Mam's store number."
1950s Co-op ad
Public Domain1950s Co-op ad
The reference to the store number suggests the boy's mother is a frequent shopper at the local Co-op. The idea of co-operative trading, where stores are run for the benefit and on behalf of their members/customers, started in the North of England where the 'divi' or 'divi number' (store number) became an integral part of the shopping experience. The dividend is a financial reward or payback for the member based on how much they bought in the stores. Historically, this was done by recording the member's number against transactions in a ledger held in each store, though when this became cumbersome the method was switched to stamps on a savings card.