interesting spare part

[RCS]

I found this rear sight base (open bottom too) at a gun show about twenty years ago. I seem
to remember there was a way to tell the Springfield from Rock Island ? maybe I am wrong

Never seen another one since.4363443635

[Fred]

Because the leg of the 7 on the leaf is curved a bit, the leaf at least is a Springfield.
Rock Island leafs had straight legged sevens. But I think you already know that.
I dont know about the sleeves.

Nice early rear sight and sleeve!!!