Kind of hard to tell (for sure) without seeing the stock style and more of the gun. Since the serial number doesn't have a letter prefix, an 'A A' date code COULD mean 'March 1954' But.maybe these will help you figure it out.
Den REMINGTON SHOTGUN SERIAL NUMBER STRUCTURE M/870 LETTER PREFIX 1950 TO APPROX 1968: NO SERIAL NUMBER PREFIX 1968 TO PRESENT: LETTERS USED (IN SEQUENCE) S-68, T-74, V-78, W-84, X-90, A-91, B-94, C-97, D-01, AB-05 LETTER SUFFIX (DESIGNATES GAGE) V 12 GA. (2 3/4”) M 12 GA. MAGNUM (3”) A 12 GA.
Feb 11, 2016 Remington Serial number look up. Here is some information that you can get from you serial number after 1921 Remington's manufactured. Elbycdio Driver Download. I have an 870.