I have a National Postal Meter, M1 carbine, that is "Blue Sky" marked. That marking saved me a lot of money and did no damage to the 'Marlin' barrel and its 'excellent condition' bore.
A caliber .30 Carbine round will insert into the muzzle, with about the thickness of a Dime, between the barrel crown and case mouth. It is a fine 'shooter' and I feel no guilt using it.
I know the carbine came back to the U.S.A. from Korea and is all GI parts. I enjoy the late accuracy enhancing features like: adjustable rear sight, 'pot-bellied' M2 stock, and wide front barrel-band/bayonet-lug.
I replaced the 'push-button' Safety, that came on it, with a rotating one. (I was accidentally releasing magazines, on occasion).
I've grown to like the birch "SA" marked stock and hand-guard.
IMHO - You have to judge returned 'Imports' on their individual merits.
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