M1 carbine appraisal question

Hello everyone, I have a question about the value of a National Postal Meter M1 Carbine that was my grandfather's during WWII. I would never think of selling it but am curious as to its value. It is a National Postal Meter M1 Carbine, with U-Stamped receiver. The entire gun is in mint condition, fired less than 50 times. The wood is perfect with only one slight dent on the grip (very minor). It has a 11-43 Buffalo Arms Barrel, seemingly all original parts. Metal Finish is 99%. I have the history of how the gun was acquired (not written by my grandfather) it was taken from an excerpt from a letter he wrote home in 1945 in which he tells how he got it. Thanks everyone.

First off let me welcome you to the site. There are a great deal of variables that go along with this carbine.

Here are some questions:
What is the serial number?
What rear sight does it have? Flip or adjustable?
What barrel band does it have? Bayonet lug or narrow band?
What stock does it have? Type II high wood, etc?
Are there any rebuild stamps on the stock?

There are so many variables. Photographs would be a huge help.

The serial number is i believe in the 4,000,000 production run of NPM. Flip sight and narrow barrel band. No rebuild stampings and low wood stock.

Without some good high res photos its not really possible to acurately advise you what you have or what its worth. Would love to see some pics, as bring back carbines are a tough find.