Here's the link to the pdf file of the 1901 Yearbook:

Quote Originally Posted by Steven Tribe View Post
For your amusement, I enclose some photos of my no. 6 400mm. You can see the Aplanat style rear housing and the original anstigmat thread for the rear cell deep down. I will check my (numerous!) Suter aplanats to see if I can find out which lens it came from.
Yes, it's very interesting to see. By looking at it, there must have been a piece of barrel added to the original, since by looking at my lens, it only has the same thread as on the front, and is not that deep. My lens group fits just fine on the front as on the back.

I measured my flange mounting thread, and it's almost 64mm and seems to be a 1.0mm thread, althoug I couldn't know the tolerances specified in that particular period. Maybe I can get a shop to build one for me, or look out for a flange with those characteristics, but of course not every seller documents everything to the full specs.