Being in Proof is based on bore size, measured at 9", and has absolutely nothing to do with wall thickness. Still being in proof does not automatically mean safe to shoot. That is my point. We put too much stock in being in proof. Holt's absolutely would not list this gun for sale, as anything except stock, action and cut barrels for sleeving unless it is in proof. That does not mean safe to shoot. They would not risk the legal problems, just for a few pounds commission. That is why they went to great pains to make sure any potential buyer knows the barrels are .006". This is a sealed bid auction and barrel thickness is not commonly listed unless thin, or a potential issue.
Call it thick or thin, 2" guns were very thin barrels to start with and it might have been .015-.017" to begin with. And another issue is where is it thin? It is not that thin at 9" where the bore is gauged, measured for proof purposes, most likely. That area, 9", might have been .020+ when new and might be near that still in that area. The barrels have been honed to remove pits in one barrel which made that one area .006" after honing. The other barrel still is .017 which I suspect was the original barrel wall thickness when new and proofed. I bet the gunsmith removed the pits and measured the gun, then found .006" and stopped. Informed the owner who decided to just cut his loss and send it to the auction house.
Holt's measures every gun they sell and list any problems like this in the description. It is always buyer beware. Sealed bids in general are cripple guns, looking for a new sucker, to pour more money into them or pay off the last owner for a bad investment. A few gems are in the thousands of listings and the fun is in finding one. They tend to be tired, worn and in this case worn out. Or they are slow moving guns, with almost no demand for them in the gun trade. I see a ton of AYA guns, model 3's and 4's that are selling for 100-300 pounds, 2's selling for about twice that, that are solid guns, with a lot of life left in them. But consider the entire double market is under a clock running out in under five years. Shoot steel by then, or it becomes a paper weight, unless you can afford Bismuth at a buck a shell or more. The double market for all but the best quality is weak and about to have the bottom drop out of it.
My best sealed bid find was a Pape 20 gauge, Hammergun, 30" barrels, choked Mod and Mod, with "barrels below recommendation". Fancy speak for thin. The barrels were .019 at 26-27" on one barrel, everywhere else they were above .020". Everything else was perfect. Or a AYA Model 4, 20 gauge, 27" barrels, I/C and Mod, with what was described as a crack in the grip. The crack, was a crack in the finish and the rest of the gun was a solid 95%. Stock refinish was all I did and it has seen tons of Clay's without any issues. That one cost me well under a grand even with importing. Or a Remington 20 bore 1100 Sporting Clays model, which cost under $800, imported, in mint condition. But these are the exceptions, not the general run of the mill sealed bid fare. Too many of them are just like this 2" gun, but not so obvious or so far gone. Out of 20 plus sealed bid buys I have missed on just one gun and it was listed as a parts gun. I sold the trigger group, stock and barrel, that more than paid for my cost. Some guns are too far gone to save. Read and understand the descriptions, ask questions if not clear.
