6536 vs 6536 (1)

[pallas1970]

Hi all, need some advice. I recently bought an old submariner from a reputable dealer on consignment. I thought it was a pretty nice 6536 (1) but on removing the band on the top of the watch body between the lugs it says Brevet + with the number 6536 underneath and on the bottom between the lugs has the number 893XX. Does this mean it is an earlier 6536, one of the 1955 ones or am i missing something? Thanks, James