US M1 Liner mystery

[Jimir]

Hi
I've recently acquired a M1 liner which is baffling me a bit.
It is a high pressure MSA liner with OD3 Kakhi webbing, blackened brass A washers, round studs for fitting a leather chin strap and an OD3 nape band with what looks like C.F.C.U female connectors.
Everything suggests late WW2, 1944 however it doesn't have a vent/insignia/ grommet hole at the front like a typical WW2 liner. Research indicates that MSA stopped making liners at the end of the war but there was one bit of information that suggested that MSA also made liners in the 50's.
Can anyone help confirm it's age?
Has anyone else come across a WW2 liner without the typical vent/insignia/grommet hole at the front?

[Jimir]

Sorry folks I've posted this on the wrong section