The 1951 - 54 (55 1st) vent window assembly is held by 5 sheet metal screws in the top section. I circled 2 of the 5 screw holes in the picture. The vent window assembly is also held by 2 screws that are accessible by removing the panel at the bottom of the door and reach inside (hard to see). 1947 to 50 doors would not have the vent window support and screw holes.
The 1951 - 54 (55 1st) door window trim will be notched to clear the vent window.
Compare your door latch area with the 1950 door (picture).
Compare your door strikers with the picture of new strikers.
A 1951 and later VIN tag is riveted to the driver's side doorpost (picture).
A 1950 and earlier VIN tag may be held by screws.
Compare your VIN tag with your title.
https://www.stovebolt.com/techtips/VIN.html
