Ever seen a Win housing marked here?

[RWB1]

"...an all original..." There's no such thing as an "all original" M1 Carbine. Winchester only made 15 of the parts including the receiver. Everybody and his brother all over the eastern U.S.made Carbine parts. Most of 'em didn't use any marks.
Go here and scroll way down to the bottom and read the 'Worth Noting' paragraph. All the menu links work too.
The U.S. Caliber .30 Carbines

There are all original carbines. You continue to say this and for the 1000th time you are wrong. Quality Hardware only made receivers , guess what, there are original Quality Hardware carbines . How they left the factory is original. As produced at the factory and unchanged in its lifetime = all original.