Nice to see new UK collectors on this forum. The numbers and letters in the small circles on some Milbros I have always assumed are mould identification marks from different moulds, other than that I don't think they have any significance. They seem to be predominantly found on the second to last type of Milbro forks which roughly coensides with the 1960s. Milbro forks mostly come in three main shape types , four if you include different lettering styles. As far as I know the unusual shape of the 'Offsets' lower handle is unique and not found on any other version.