I never owned one of that age - look at the top of the rear tang, behind the hammer - some lever guns had two holes there - one (rear one) was a bolt that went through to hold the butt stock on - second one - further up, I think just had a "plug" in it. Was for specific tang sights that folded up and down. If you do not have two holes on top of tang, nor two holes into side of the receiver, I do not know how to get a rear aperture sight without drill and tap...
Yup mine is just that. For a few years in between like mines, no tang holes and no side holes above hammer screw. Sucks for me I guess.




















































