Having read the article, I was puzzled by the top paragraph on page 78. Ed talks about multi-block movable doors vs the single block doors that Lionel used at different times.
I have carefully compared photo 9 with 10 and 9a with 10a and I guess I need new glasses because I cannot see any significant visible differences that jump out.
So maybe someone with a digital edition can copy the pictures and put arrows pointing out where the differences are. Or if there is no difference, then what is meant by multi-block and single block doors?