42a and 751 Police Telephone Box (1936-60)

Here are two of my three Police huts and a photograph of the inside.At the bottom of the model details underneath the roof there is a marking: C 8 2 (or 5) Does this mean a mould with 8 cavities or something else?All three of my huts are marked in the same way, has anyone seen any variations on this marking?

Resized photograph

I have two post war examples with C82 inside, so perhaps not a cavity number. My pre-war example does not have this code in it. So perhaps a way of distinguishing pre-war from post war examples.