I've read through the black bayo hypothesis and I must say there is not much data backing it up at all. It's a pretty good stretch to make a claim that they were built early but then never used until the original builds of late guns happened. I find it much more common to see the golden tinted bayos on 'as-issued' '56-'58 guns. I've been freshening up the Russian S/N database for the past few weeks and still have several hundred guns to catalogue, but once it's done maybe I can toss out hard data to see what's most plausible...
Irregardless, that's a nice gun OP. I'd be proud to have that one in my collection, regardless of the refurb.