Harold
I checked my ‘46 and both doors also have those holes. Out of curiosity I checked my ‘37 and the doors have two holes each but only about 1/4 inch in diameter. As you found, there aren’t any threads and each hole had a piece of metal at or almost touching the backside of each hole. I don’t know the purpose of these. My guess is they served someway during the production line run? There doesn’t seem to be near enough meat there to grasp a rubber bumper and have it stay in place for long.