It is clearly an arsenal rebuild. Vast majority of them were.
When WWII started the military was woefully ill equipped..
The Garand didn't see field use until sometime in later 1942. Even then the Marines issued the 1903 as they thought the Garand wasted ammo. The Garand only seeing use in the Pacific after the first major campaigns.
National Guard units assigned duty at US bases were even issued Springfield Trapdoors for a while.
It is highly likely that your gun saw heavy service until being returned for rebuild in late 1944 or later.
Remember that for a long time the ammo was loaded with corrosive primers. Barrel.date was the earliest it would have been rebuilt. Early guns were heat treaded by hand and there are those who recommend not shooting low serial number guns. Here again there us some debate. Some say less than 750,000 and some say 1,000,000
FWIW, I had an early gun (1909) and parkerizing was light
By August 7 when the Marines went ashore on Guadalcanal they had several hundred garands with them. At that time the whole USMC had garands except for the 2 infantry divisions as they were already forward deployed. By early '43 it was fully equipped with garands.
