I have had the SKS for 15+ years and shortly after I got the rifle i purchased a bunch of ammo and a scope mount built into a dust cover. I think I got the mount from CDNN, I am not 100% sure on that as it has been a while.

The mount has no markings at all inside or out.

It is a dust cover with built in scope mount. There is a screw on the back covered by a knob turret style cover. The screw removes wobble between the dust cover/mount and the rifle. There is a lug on the inside that the pin holding the dust cover in place passes through. The lug moves forward or backward depending on how you twist the screw. Since the pin holding the the dust cover on passes through the lug this will tighten or loosen the fit and thus remove or produce wobble.  

Here is the mount:
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Here is the adjustment screw on the back and a close up of the lug:
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Mounted on a buddies gun:
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So the question is, what do I have here?

I think you got the Holy Grail.  That is reputably the only type of dust cover scope mount that will actually hold zero without having to drill into the receiver.  Lucky you.  I don't know the brand.  There used to be a thread on sksboards.com that showed all the different makes of mounts, but now with the photobucket fiasco it's impossible to find the right thread.  

Looking forward to hearing a range report.

I had a feeling it was a holy grail, I just wish i could find out more about it.
My buddy ended up in contact with a guy in Russia that used to be in the military. He could not provide any info on this mount either.