1) These inserts were used to change shotgun barrels to rifle calibers. This one came with a Remington Lift Lever Shotgun. Remington advertised them in their catalogs from the 1870s to 1903, but they are seldom seen today. Excellent with 95% nickel overall, worn only on the knurled nut at the front and the front of the chamber. The extractor is missing. 2) Marked "40-50 STRAIGHT 12" on one sid e, behind the serial number on the reduced section of the barrel in front of the chamber. The chamber section is 2-1/2 inches long and has a sliding extractor which lines up with the one in the barrel. A knurled ring at the muzzle centers the barrel in the shotgun bore and tightens the auxiliary barrel. This piece is normally missing if the barrel is found loose. Remington carried these in their catalog from the 1870s to 1903 but they are seldom seen. The caliber was popular in the 1870s. Fine with minor spotting and light surface rust. The bore is bright with widely scattered frosting.