Mine was like the top pictures with the short rail. Mine was a heavy barrel that is something like 28 inches long and about .97 at the muzzle. It is stamped U.S. above the serial number and no, my bolt did not match the serial number.
From what I understand, they pulled all the bolts and put them in a box. When a gun sold, they would just grab a bolt and put it in and send it. I had to put a .008 shim between the bolt half's in order to get mine to headspace and fire.
I have the barrel off of mine right now and have set it back 3 threads and I'm going to cut and freshen up the chamber.
