I bought a used Remington 521-T that has a globe front sight that I suspect is a Lyman #17 but have no way to tell for sure. I had new a 521-T back in the late’50s but it had what I think is known as a partridge sight on it along with the Lyman aperture micrometer rear sight. There are insert kits for several Lyman globe sights but I have no way of knowing the difference between them. I’d like something other than the insert that I have now, a crossbar with circle in the middle, I understand they have different inserts with different size circles for use with different size bullseye diameter and distances as well as 2 with different size post inserts. I’m not going to be competitive shooting with it so I’d like to be able to change the insert or maybe just remove it and put a partridge post on instead. Any idea where I’d find one of those? Brownell’s doesn’t have anything. Haven’t checked Numrich/ Gun Parts yet but that’s my next place to look.