I am the current owner of this gun having acquired it from Amoskeag during a recent auction. I finally had a free afternoon so I disassembled the gun. I can report the following after a hands on, in person inspection:
1. the barrel is a military barrel and is stamped "s".
2. all of the upper internals are marked savage, except the blish which is stamped AOC
3. the ejector is a smooth savage marked one piece ejector.
4. the compensator is a military compensator and was refinished at some point in time as significant pitting is visible under the parkerized finish
5. I believe the receiver to be a late Colt production receiver. the machining for the drum access is identical to the colt receivers to which i compared this receiver and is easily distinguishable from the recesses seen on the early Savage receivers to which I compared this receiver. the fit and finish of the machining on the inside of the receiver is identical to other Colt receivers to which I compared this receiver. the font and spacing for all of the receiver markings (other than model and serial number) is identical to the Colt receivers I compared.
6. the lower receiver is not numbered. although i did not disassemble the lower, all of the lower parts appear to be Savage. the trigger is a Savage trigger based on comparisons to other Colts and Savages .
7. the grip mount is savage marked
8. the Lyman sight is military based on the USA spread and rough finish
9. the rivets are not flush with the base of the sight. they are rounded and protrude.
10. the foregrip is Colt. the pistol grip is moline. the rear stock is early savage. butt plate is numbered to the wood. slide latch is numbered.
11. there is no secret serial number. the is a letter "N" stamped in the recess where the end of the grip mount fits against the receiver. this is the only marking on the inside of the receiver
12. the area under the grip mount is in the white. the threading in the receiver for the barrel is in the white. the face of the receiver nose behind the barrel is in the white. the inside of the receiver is fully blued and the bottom of the sight rivets are not visible in the receiver. I conclude that the upper receiver was not refinished. rather, it was blued with the grip mount and barrel and Lyman sight all attached.
13. other than the "N" under the grip mount, there is not a single letter, stamp or other mark inside the upper receiver.
14. I could find no letters, stamps or other identifying markings at all anywhere on the lower receiver--even under the pistol grip.
15. the US and A1 markings were applied using a different process than the NO.13159B markings. the application of the US and A1 markings were applied with significant pressure/force as there is a noticeable indentation in the receiver under the US and under the A1.
16. the US marking appears to be a single marking and the A1 marking also appears to be a single marking. (i.e., the U and S applied at the same time and the A and the 1 applied at the same time).
17. the US marking font and location is consistent with the US marking on a military savage I have (other than the double strike). the A1 marking is not, however consistent. the A is a different font and the 1 is also different.
18. the serial number appears to have been hand stamped, very lightly, one number/digit at a time. the 3, 5 and the 9 are incomplete. they are also not on the same horizontal plane.
19.the paperwork (form 4) shows the model number as 1928A1. the manufacturer is listed as Colt Patent Firearms Co., Hartford, CT USA.
If there are additional questions, I would be happy to try to answer.