The upper pictured below came to me mounted on an M16 registered receiver. I put about 1000 rounds through it and it ran fine. The barrel, however, is about wore out. I checked it on a throat erosion gauge and it did not register. The bolt did not lock on a USGI headspace field gauge. The M16 bolt group is a no-name as far as I can tell (didn't bother cleaning the carbon off the bolt to see if there were any markings). The barrel is blued with no markings (there may be marking under the handguards). There do not appear to be any forge marks on the upper.