1951 was the first year for the vent windows, the 51's still had the pull down exterior door handles. The vent windows were the standard on the 51, 52, 53 and 54. Either your 53 without vent windows isn't a 53, doors have been replaced or the vent window have been removed. Does it have pull down door handles or push button? If it has pull down handles, the doors are pre 52.
