So I've stipped my carbine and while I cleaned it I jotted down all the different proof marks I could find and tried to research what they all meant.
Here is what I came up with so far.
•Receiver: Inland 53426xx
•Barrel: Marked “Inland Mfg, Div. General Motors 7/44”
•Bolt: Marked “OI” (Overton Co.) correct for Inland
•Slide: Type 5 Marked “7160091” and “B” on bottom, marked “PI” on inside (Packard Manufacturing Co. of Indianapolis) correct for Inland.
•Trigger Housing: Marked “Inland”
•Hammer: Marked “HI” (Hemphill Co.) correct for Inland
•Handguard: type 1 marked “OI” (Overton Co.) correct for Inland
•Stock: Marked “UEF” next to a Springfield logo and stamped with a “P” on the bottom of the grip.
•Buttplate: Underwood pattern
•Barrel Band: Unidentified proof mark
•Recoil Plate: Underwood marked “.u.”
•Front Sight: Marked “N” (Niedner Rifle Corp. of Dowagiac, MI) correct for Inland.
•Rear Sight: Type 3 marked “I.R. Co.” and numbered “7160060” (International Register Co. of Chicago, IL) correct for Inland
Forgot to mention the mag proofs indicate that three are Winchester, one is Union Hardware, one is Rock-Ola and one is Inland.