? about a barrel

I have a barrel marked SA F6535448 NM 9 54 A214A "DOD stamp" The NM looks like it was stamped later as it is not in line with the rest of the lettering and below the NM is a "P". I always thought National Match barrels were stamped down by the gas cylinder? This barrel is on a CMP gun TE 4.75 MW 1.5


Thanks
Chris

Here is a pic of it.


https://www.milsurps.com/images/impo...ry3D400-22.jpg

I don't claim to know NM rifles, but the part number is a standard barrel identifier. Maybe it was stamped NM because it met NM specifications. I have seen LRM barrels with the part number milled out and re-stamped with the NM part number. Two NM numbers are 7790134, and 7790135.