HSTE[Omega Moderator]
4572
I think there are a very few "oddities" within the "Bund" productions. I have had ...
... all Bund variations with mechanical movements (I did not bother about the Quartz versions).
If you study the specific literature (a lot of it in German speaking watch forums), you will see that ref. 3501 is on the official and comprehensive list of "Bund" variations, later followed by the 3509, the 3529 and the 3519AMG. What is odd on your example though is that 3501 should have the military number ending on 197-8096 and not 197-9681. But again, I think there were some very few odd combinations.
I for example own what is nicknamed the "Bund-Executives": it has all the "Bund" attributes and it has the 3509 reference number inside the caseback (which was exclusively for "Bund" watches) but there is no military number on the outside of the case. The story there goes that IWC made a handful of "Bund" examples for some executives of Porsche-Design in Salzburg.
Cheers, HSTE