Take the serial number off the bottom of the grip butt.
I guess it has been removed. There is no blueing on the butt and its not exactly flush with the bottom of the grips. They did a good job grinding it off though only numbers are in front of the chamber. MOD 10-5 on the frame connecting the barrel. 5617X on the chamber arm with QG-5 underneath the Q.
Unfortunately your gun now may have some legal issues with the serial number removed. The other numbers are assembly numbers and instector initials.
That said, 10-5's were made from 1962 to 1977.