Had to replace one of mine on a 99t rifle. The two main types were Marbles and Lyman From what I have seen, the Marbles sights had the locking nut and the Lyman did not. Also, The Lymans have a little lever on the side for the fold down feature and the Marbles have a small pull tab at rear of sight that you pull out to fold down. .
Mine was a Lyman and the up/down stem was stripped, traded it in for another . Most all the ones I have seen had a makers stamp on them. The Marbles sights have it marked on the lower side in very small letters, sometimes hard to see. Does the person who is giving you the trade in have the exact replacement one you need ? It maybe worth it if it is the same type that you need. Check out EBay, they usually have a few listed on there.
Last edited by monty852; 01/16/20.
