Remington 12, late 1920’s somewhere in the 650000 - 700000 serial range with retainer screws on main forend grip screws. I suspect with a later vintage Remington peep sight, I suspect. I quite like the look.
I am fairly certain, the sights are Remington, possibly 1940’s or '30s. Maybe? If someone can pin point the exact model and what not, it’d be appreciated.
I originally bought it for giggles, because it was $50, but it’s actually been pretty useful for teaching new shooters. I’ve introduced a couple of people to shooting with it before the whole lockdown thing started.
It’s a nice basic single shot, that you need to manually cock, so it’s been great for explaining how guns work.
Sounds like you are right. https://gun-data.com/winchester_Model_1890.htm.
Out of interest have you tried shorts or longs in it?
My 1906 and 62 will feed all happily, apparently 1890’s are length specific, unless its had some parts swapped.