This Remington manufactured late variation receiver insert is for the model 550-1 semi-auto rimfire rifle and is in very good condition with light wear.  (file photo)

Note: Remington model 550-1 semi-auto rimfire rifles with the following date codes and years of manufacture have been observed with this part: (DUU) Sept 49, (EUU) Oct. 49, (CWW) Apr. 50, (RYY) Nov. 52, (PZZ) June 53, (LB) Feb. 55, (WB) Aug. 55, (XD) Dec. 57 & (DS) Sept. 69.