The M2 Rifle stocks went into production in 1932. The NBA Sporter was produced in 1926. The NBA Sporter stock had the extreme drop at the butt like the 1922M1 Issue Type Stock. The M2 on the pistol grip tells us that it is an M2 stock to which someone has added the crossbolts. M2 Rifle stocks are often seen on 1903 rifles but without the crossbolts. This was a quick way to use an available stock to sporterize a 1903.