Well you do know the stock has been replaced, possibly done at the Armory level with 'spare parts' stock.
Wondering if the barrel and receiver are original mates.
NPM used many barrels. If that U barrel is original to the NPM receiver it would have what we call the NPM punch mark near the P proof stamp on the barrel.
Note Pictures by fellow member mpd1978 showing the NPM punch mark (proof)....
Help needed for correct barrel for NPM
Cheers,
Charlie-Painter777