Hi Jeremy,
Welcome to the forum. I split your topic off from that old 2015 thread.
What I can tell you about your carbine:
- 1956 built. Receiver cover should be blank like it is. Whether it was manufactured blank or a scrubbed Tula/Izhevsk stamp is debatable. It could be either (though it certainly looks odd in the center doesn't it?)
- It is a refurb with a mismatched stock and it appears to have been reblued (the whole gun, not just the receiver cover.)
- Components were likely all built at Tula, but there is no hard data that says the carbine was actually assembled there. Could have been at a smaller facility that has been hypothesized but we don't know anything about.
- Hex marking to the left of the receiver S/N is a refurb marking.
For the receiver cover, it would help to compare the font of the S/N with the font on the rest of the carbine. I'd lean towards this is a replacement blank cover off of a different letter series carbine that was scrubbed, reblued, and paired with yours, but w/o seeing more it is impossible to tell. I do know that a 1956 TO that is 4500 units in the build was not the first prefix produced, and is extremely unlikely to have had the receiver cover top markings scrubbed at the intiial build from a 1955 cover that was previously marked like we see on some of the other prefixes. Additionally, from my observations, we don't see the top markings scrubbed on older covers during refurb, they left the tops as-is while scrubbing or XXXing out the S/N.