Well, I got the rifle in hand today. This is a marvelous little double rifle. Action is tight as new when made in the 1890s, and it operates silky smooth. There is no doubt - this is a center-fire cartridge double rifle as witnessed by a chamber cast. Its in 11.15x60R caliber (43 Mauser) I can't wait to take it to the range to see how it shoots. But it may be a while. Outdoor temperature were 10 degrees today.

https://www.buckstix.com/buckpics/43-cast.jpg