John, Congratulations on your find. The bolt should have the serial number etched in electric pencil on the top, visible when the bolt is closed. The barrel date should be stamped behind the front sight. It will be something like 4 27 (April 1927).
The most common modification to these rifles is shortening the stock and/or installing a recoil pad. The NRA Sporters were not modified military 1903's, they were made up from new receivers to be sold as NRA Sporters. Unless you know how to clean the rifle without removing the finish on the metal or wood, I suggest get expert advice before any cleaning is attempted. I am looking forward to seeing pictures of the rifle.
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