Might it be lead buildup from the boolits?
I think people have posted here before that their blue/nickel was coming off, but it turned out to be lead and powder residue fused to the cylinder.
From the pics, It looks like johngross hit the nail on the head. I have had similar buildup on my new SAA from shooting factory loads that were a little hotter than cowboy loads. It looked like it took the bluing off BUT after some careful cleaning, it came right off -it was residue from shooting.
The guy said he fired it twice and this happened
I'm confident that johngross is correct that this is powder/lead residue build-up; the pattern of flaking is exactly the same as the powder/lead residue that you see on any blued gun. Nickle is not going to flake off from firing a few rounds through the gun. If the nickle plating was that poorly done, you would see chipping and flaking on the hammer, trigger, cylinder bolt and other moving parts.The guy said he fired it twice and this happened
Yes, I know what part to the cylinder the OP meant. This appears to be typical powder/lead residue build-up. I get this a lot, particularly when shooting lead bullets. I have an old K-22 that's a real PIB to clean this off of.I'd say this is flaking and not powder burns. OP is talking about the side of the cylinder between the flutes and not the face of the cylinder. Some pics the gun is shown with OEM gen II stocks and some with aftermarket stocks.