I would think that all original cams have numbers cast into them. This should then be comparable to original part numbers as shown in the BMC parts catalogs (manufacturer's books, not Moss, VB, etc.). I am speculating, as I've never attempted to verify such (though I could probably find a cam somewhere in the shop, given the time...).
If it's a reground cam, like Bob's Racer Brown, or my own Isky, then yes, typically engraved on the end with the regrinder's part number, like mine seen below (an original cam should be plain__no engraving on end).