A LOT of M14 mags out there and a LOT of them are fake USGI. If I can't see it, hold it, and check out the welds on the spline, tab and follower, I consider them to be fakes. Sounds bad but it's the truth. Any packaged in white "bags" are probably fakes. Any with unevenly spaced welds up the spline are fakes, and any W marked needs to be cked out carefully. Thanks to a great sticky at THE m-14 site I saved a crapload of money staying away from fakes. Got some very nice real USGI ones instead.
That goofy muzzle device seems to have a pretty good rep for being a reasonably good working comp.