It is serial number 374XXXX, which puts its date of manufacture in April or May 1945 at the Springfield Armory.
The top number is the "heat lot" of the steel from which the receiver was made. The lower number is the drawing number and revision number, in this case revision #35. The discoloration at the rear of the lug may be due to a "lead bath draw" in which the receiver was immersed into a bath of molten lead to prevent cracking.
The bolt also is stamped with its drawing number and revision number, and below that, the heat lot of the steel.
This picture shows the operating rod. It does not have the "relief cut" found on post-WWII Garands. This is the "straight-cut, curved-side" version of the op-rod. I haven't been able to find a drawing number on it.
The trigger group is also marked with the drawing number and revision number. Note the "cloverleaf" hole in the lower right, between the trigger and the safety. Some of the trigger group parts are interchangable with the M-14/M1A. An extremely clever design! A lot of thought went into the trigger group and the results were spectacularly successful, especially for a mass-produced, "government contract" battle rifle made during wartime. Springfield Armory and Winchester made four million Garands during WWII, and at peak production, in January 1944, they were producing 4,500 rifles per day!
The stock doesn't have any markings or cartouches that I have been able to see. Even using Photoshop (well, GIMP, actually, 'cause I'm a Linux geek) to magnify and boost the contrast, I can't see any cartouches.
I have a copy of Scott Duff's book, The M1 Garand: World War II, and as far as I can see, this gun is as it left the factory in 1945. It doesn't appear to have been "armoried". All of the parts and their drawing numbers are contemporaneous to the date of the serial number. I haven't taken it down beyond field-stripping it, and perhaps there is some non-original part lurking somewhere deep inside it. The trigger group parts are often individually marked, but I'm not opening it up to find out! I have a Brownell's tool for assembly/disassembly of the bolt, but that's as far as I go in the "shade-tree gunsmith" department.
It shoots well, too. I haven't put more than 50 rounds through it since I bought it. I do need to sight it in. When I got it there was caked cosmoline on the front sight and I had to disassemble it to clean it, and that has thrown off the point of impact.
One of "liberty's teeth". I wonder if it nailed any of freedom's enemies; I wonder if it will again?