Rick,
I have the Van Wyngarden book as well and agree, there is no inspection window that I can discern. In the Leaman book there is a photo of 10217 from a near identical angle with MvR and Gen. von Lossberg (top of page 47), and no inspection window that I can see. Based on these photos I`d say you are correct, it wasn`t there on these first two put into service.
Cheers,
Lance