the only ones i'm familiar with are the m7 shoulder and the m3 flap, and the m1912 - you can look those up in your search engine- i don't think there were any new designs in the 50s- the m3 and m1912s are belt flaps, and the 1912 has a pivot so you can ride a horse - ie it looks like a drop leg, but it's really just a belt with an extension- once you start involving "civilains" you get all kinds of abominations