Remember that the Sideplate Stevens seem to have had multiple patent dates that could have introduced the cartridge. I have seen or read about 1885 and 1890.

What would make the most sense for the 25 RF would be to have been introduced with the Stevens favorite 1889 patent. New rifle, new cartridge, in 1889/90.

By shear luck I had the chance to meet Lou Behling last Saturday at a gun show. So of course I had to bring up the 25 Stevens. I asked specifically about Peters and the claim of them developing the cartridge being unlikely, since they were a brand new company. To his knowledge, Peters only made shot shells until the mid 1890’s, then started with metallic cartridges.

Sure shot wrote on Aug 8^th, 2023 at 2:29pm:

I think that’s correct. Mr. Behling was pretty confident. 
His response to the Peters question was basically “they weren’t even making metallic shells until the mid 90’s”.

I would be interested to know what rifle/pistol it was first offered, or across the whole line.