This Winchester manufactured third variation 30-B series rear sight leaf with the "V" shaped sighting notch, 5/8" side wings, and patent dates is for the circa 1912 or earlier manufactured model 1890 slide action rimfire rifle. The condition is very good exhibiting a brownish gray patina with light wear. (file photo)

Note: Winchester model 1890 slide action rimfire rifles with the following calibers and serial numbers have been observed with this part:

22 Short:

22 Long: 790566

22 W.R.F.: