Toby,

It is extremely unlikely that an 1892 vintage Model 1873 was factory fitted for a sound suppressor (silencer). Maxim was one of the first (if not the first) commercial makers of silencers, and they did not begin making them until circa 1907.

If you can post pictures of your rifle with the cap installed and removed, we might be able to provide more information.

Bert

podufa said
I can’t find where he said it is a Model 1873 looks like he called it a Model 1892  

Right you are… I have no idea where my mind was wandering when I read his post

Bert