Well I'll be damned. I wonder why no sales between the wars? That bike reminds me of a Zundapp. Do they share parentage?
According to Wikipedia's article on Zündapp's KS 750 at
https://en.m.wikipedia.org/wiki/Z%C3%BCndapp_KS_750 , the heavy hand of the wartime Wehrmacht was the motive factor in the similarities between it and BMW's R75 model. In fact, they wanted BMW to just produce the Zündapp model, which they much preferred in tests, but finally settled for interchangibility of many parts. Hence the resemblance.
I was lucky enough just a couple of years ago to enjoy a nice long day's jaunt through the southern Ohio countryside on a buddy's '50s Zündapp KS601 "Green Elephant", basically the peacetime descendant of their KS701, and also, more briefly, on his mid-90s BMW R100RS, the very last of its big "Airheads", and I felt MUCH more at home on the Zündapp. Any Bullet owner with the wherewithal to get their hands on one of those big Zündapps would do well to do so.
And to our original poster David: Should you have any serious hankering of getting that beast of yours running, shoot me a PM, and I'll be happy to share my buddy's contact info. He's basically "Mr. Zündapp" in North America and might well be crucial if that thing's ever to thump along again. My German's also pretty fair, if you think that might help with needed parts contacts and such.