I looked that thing over well and I gotta say, without some sort of authentication.....no way it sells for that. THey are fishing for a sucker. I remember a few years back when the "craze" was at its peak a few of the no shit verified originals came out of the wood work and those sold for like 8-10k for a collector that is a prize but I'm skeptical to say the least. Logistically it just doesn't add up. With so few of them ordered and issued, why would this one be unissued? Remain in new condition for nearly 50 years? Sorry guys, I smell a rat.
Also in this day and time it is quite possible to assemble a replica from available parts. Some of the parts (correct scope) are rare to say the least but they are out there. It could be made on a reciever with the correct vintage serial number, restored and claimed to be unissued. No one and I mean that.....NO ONE would be able to say with 100 percent certainty that it wasn't what they claim. Now then, I've seen Marine Corps equipment and to say the least they are used hard and put up wet. I would approach that thing from down wind.