The lower windlace that attaches at the step was changed in 1950. The '47 to '49 is what is shown on the Steele document. The retainer screws into the vertical part while sneaking your screwdriver up under the rubber. I'm wondering if a similar change was made to the door weatherstrip during that time and has been long forgotten?
I didn't know there was a change on the lower windlace mounting. I'll file that info away.
My '51 has the same lower weatherstrip retainers on the doors as you've pictured, so I don't think there was a change to that. I believe it's there just to keep the weatherstrip more secure than just glue would be.