Dating one liners
and Firestone ceased the production before or at the end of the war.
All other high pressure liner: Westinghouse, MSA and Capac were produced after 1950 too.
However straps OD#3 can be found in rear seam late war examples too. Late war helmets have a blackened brass buckle with simplified design.
Since September 1944 a new release hook, called T1 was adopted and seldomly mounted, though it became a standard only on years '50s production.
The use of clasps is postwar.2) all shells with the rim that has the seam in front have been produced during WW2, from April 1941 to November 1944, either fixed or swivel bails.
Then the seam moved to the rear until August 1945 when production ceased.3) the production of M1 shells started over in 1951, so how can we recognize a late war from a postwar?
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.
History: Sets of dentures have been found dating from the 15th century and probably existed before that time.The leather chinstrap: another component that can help to date a liner is the leather chinstrap.All postwar chinstraps are made of blackened steel, are marked DOT on the rivets and usually bear a anchor under the flip tab of the buckle.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.It is not easy to tell if the repainting of a shell dates back to WW2 or later, other clues can help like the stitching on the straps and the liner.
There is a lot of Important Denture Information here to look at.