The Nambu pistol as well as the standard Ruger MK II , Mark I , II , and III entered the US firearms market in 1949 .
and although he decided against marketing them , the handgun 's rear cocking device and the Nambu 's silhouette was incorporated into one of the most popular .22 semi-automatic pistols to ever enter the US firearms market , when in 1949 the [ [ Ruger MK II | Ruger Standard ] ( and later Mark I , II , and III ) pistols were sold to the US public.