As others have said, what your nephew has is a sporterized 03A3 made by Remington. The USGI 03A3's were made by Remington and Smith Corona (Yes the typewriter Co.) Smith was also the same Smith in L.C.Smith the maker of fine side by side shotguns...I digress.
Back to the 03A3's....They are a very strong and reliable action and should provide years of good service. As stated a nice example in "correct" military configuration will fetch up wards of $750.00 - $1,000.00. An all original, never taken apart, never been through an arsenal (most have) will fetch quite a bit more.To find an unaltered example is rare indeed. Most think they have an original but you would be surprised how many "tell tale" signs will let an experienced collector know it's not.
I have both in my collection (sporterized and USGI configuration) I prefer the originals better but I've had to "rescue" some pretty rough "bubba" jobs over the years. I put a whole lot of money into them....far more than I could ever get back selling them but they turned out to be great hunting rifles.
Tell your nephew congrats on a great rifle.
Here is a Smith Corona 03A3 re chambered to .300 Win Mag. The receiver and barrel are both USGI original and this rifle shoots like a dream! Yep it's a super strong action!
Another pic...
Here a couple more sporters...
Remington 03A3 with original USGI .30-06 barrel
Here is a Cech Mauser re barreled to .270
This last pic is how I prefer my 1903's and 03A3's.....
