Dating search cork
Also they were fitted with a rim that lost the paint showing the brightness of the stainless steel it was made of.
Since the production began, until 1943 the colour of the straps attached to the shell was the olive drab #3, from 1943, mostly on Schlueters, the shells started to be fitted with straps colour olive drab #7. Mid war helmets were fitted with blackend steel buckle with simplified design.
Most of US M1 in use during the Korean War up to early Vietnam War were produced during WW2 and then repainted, fitted with new straps and new liner.
Wartime shells are a little taller, in a darker shade of green.Under the brim there is a number indicating the production lot.