Hello Harry ...

I am looking at Michael firearms spreadsheet and there isn't a lot of detail to go on. I see a few Borchardts on his list ...
1)Niedner's Borchardt Pope 38-72;
2)Niedner-Baker Borchardt (but no caliber or serial number);
3)custom Borchardt Long-Range by John Wills .45-70;
4)Borchardt .25 Krag

I don't know if rifle no.4 listed above was a Niedner rifle or not.

... Joe