The serial number is not what tells you this information. It's the 2 letter code on the barrel. this tells you when it was proofed, not when it was made.
A=0, B=1, C=2, D=3, E=4, F=5, G=6, H=7, J=8, K=9
I found this information online.
This is for guns proofed before shipped to US.
If gun was sent w/out being proofed, code wont be stamped on barrel