Classic steel Sheridan PGP or PMI 1 back sight, excellent shape, light light screw wear and some have light rust that can be rubbed off with hand. Are blued. Has round end. Came off PGPs at Mac 1 that that were being converted to Annihilators. Sat in box for 25 years. Also works on PMI2. Some also came from Gramps and Grizzly's.