You have pointed me in several directions and I'm finding ALOT!
Went back to Mr. Petrov's post in '01 (
https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=197299) and found a Linden/Koshollek where the pistol grip cap is an exact match for this one.
I will say Mr. Petrov seemed to be a great researcher and knowledgeable as all hell. Appreciate the direction, I will look at some of my shops books tomorrow & see if we have any Linden books. I've got several new books on my watchlist as well. Waiting on 'The Modern Gunsmith' 1& 2 to be delivered this week.