I have just picked this US made shell and liner as a 'Korean War era M1'. The shell is a rear seam swivel bale. There is no chinstraps. The texture appears finer than WWII era examples I have. The paint seams to be original and is what I believe is pre-Vietnam era OD. The liner is a Westinghouse/Capac 51 with post WWII webbing.
The liner is definitely correct for Korean war era - I am not yet convinced about the shell. Any opinions are very welcome! Thanks