the shell seems to be ww2
the inlet post ww2
inlet is called a 'liner'. And you are correct mike these liners date from the vietnam era.
sorry my broken english...
Hello, IMHO the shell is certainly WW2, it has the brim seam in the front. Lots of WW2 pots were reused for the Korean/Vietnam wars. Chinstraps are post WW2, as they are attatched with steel clips to the helmet, rather than being sewn on. The liner is probably post Vietnam, as it is the snap in type, and is maybe from the very late seventies to eighties, as vietnam era liners have the WW2 type A washer system for attatchment.