I have checked various posts and websites with listings of serial numbers but I am not really certain what year my gun was manufactured. So I will turn to the experts on this forum. Here are pictures of the barrel and receiver markings. Thanks for the help.
Easy Peasy! The "1M" above the serial number stands for 1961 and standard weight 12 as opposed to the "G" of a Light Twelve. http://www.nramuseum.org/media/940941/serialization-date of manufacture.pdf
