A fine effort by your significate other. How long is the brass and do you have any other that is shorter? On modern ammo you may have to resize the brass as if you get it in you will have do disassemble the longarm and punch it out. The initials "R.Z" on the right tube I'd guess to be for R. Zimmerman, barrel specialist, of Suhl. As for all the "K"s, it's pretty much a toss up seeing there were several but I'd look toward Edmund Keller of Zella-Mehlis, Oscar Kirchner, one of the Königs or one of the
Klett's(highest probability) like Heinrich Christoph
Klett or his son Heinrich Louis
Klett.
Kind Regards,
Raimey
rse