Hank15 on another forum has an old standard weight 1100 built on the 12 gauge sized frame that has serial number 478362X and no letter prefix. The first letter identifies the month and the second letter identifies the year of the manufacture of the barrel. There is a two letter code located on the left side of your barrel near the frame. Before the RemChoke system was introduced in 1987 for the 20 gauge 1100, shooters often owned more than one 1100 barrel (understanding that the LW and LT barrels did not interchange with an older standard weight barrel like you have). To get a specific year of manufacture, please call the Remington Help Center 1-80 M-F 9-5 EST with your serial number and tell them that it is a 20 gauge 1100.Īfter that, you can check if the barrel is original. From then until 1968, there was no serial number prefix. The 20 gauge 1100 was introduced in 1964. You need the letter prefix of your serial number to get a general range of years for when your 1100 was manufactured. This X designation ended when the "heavy frame" (built on 12 gauge sized frames) 20 gauge 1100 guns were discontinued in 1977, so your gun was manufactured before 1978. The X at the end of your serial number is called its suffix and it designated "20 Gauge Heavy Frame (discontinued)".