Like Jim said its in the transition area ,
IMO if its a narrow rib K22 in bright blue its fairly uncommon (am guessing it is a narrow rib with K250 xxx serial)
While the new weight matched wider rib version appears in the 1950 AMC IIRC those dont seem to ship until mid to late 1955 (my earliest bright blue wide rib is K259xx shipped June 1956).