Hard to say, I haven't called Remington to confirm yet (though I dont mind if you'd like to know).
The serial number on the reciever is 141848V, which places it somewhere between 1963-1968 as they added a letter prefix after 1968.
To my knowledge, the barrel has been changed, so we can't date...
For sale or trade is a 1963-1968 Remington 1100 12ga 2 3/4" semi-auto shotgun, with 30" FULL Barrel. Has a quick(ish) detachable leather sling. Gun is in great condition and functions perfectly. Only issue is one small scratch on the forend. Comes with soft travel case and a silicone gun sock...