402 Bedford TK truck 'Coca-Cola' (1966-69)

Does anyone know why the chassis (actually the flat bed or base of the tray holding the crates)for the 402 Bedford Coca-Cola truck has either the letter 'A' or 'B' below wording COCA-COLA? The 'A' example appears to be more common than the 'B' version, or at least that is what I have noticed. Here is one with the letter 'A' And with the letter 'B'

I expect it is a die identification,
this way if one of the dies started to develop faults it would make it easier to identify which one was with an issue.Kind regards,
Stef