I have a Mauser 71 Jager rifle with inscribed to Lt. Denis too. I've just been doing some research on it and it appears to have been manufactured in 1880 or 1882 (both dates on the rear of the receiver. The inscription reads: L, F, & P on top with Lt. Denis underneath. This was my grandfathers until a few years ago. There are a number of "I under crown" proof marks on various parts of the receiver. I'm very interested to know who Lt. Denis was.
The serial numbers on the action are all 80026.
Sorry I can't so much but ask more questions but maybe this rings a bell for someone.