(This does not make sence on mine I am looking at 2 M40's they both have NOO. Serial #77XX shows a date stamp 2.5/00, serial #102XX shows date stamp 2/00. 2500 difference in serial # 2 weeks difference in date stamp and something in reverse order.)
Now this does make sence frames were made in Feb 2000 and weapon was proofed Mar 2000.
Inside the dust cover there is a circle with 1-12 and and an arrow in the middle pointing to month it was molded on each side of the arrow is two digits indicating the year