Hull Identification number - there might still be something scrawled in felt tip up the bow giving the date etc but don't hold your breath because I don't think Normans were ever offered with a build history requiring HIN.
Better chance might be the safety glass etchings if it's Triplex Toughened in the windows, we used to be able to date old cars within the decade (you guessed the decade) with that.
Otherwise take a flyer - I assume it's for insurance purposes?