This Remington manufactured open (rear) sight leaf is for the model 550-1 semi-auto rimfire rifle and is in very good condition with some light surface rust specks.  (file photo)

Note: Model 550-1 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, (EWW) October 1950, (LXX) February 1951, (WXX) August 1951, (LYY) February 1952, (RYY) Nov. 52, (PZZ) June 53, (LB) Feb. 55  (WB) Aug. 55.