If they are from Bonhams, they will be 'in proof', though by how much, one can't say. If you want a gun to own and use very occasionally, 0.019 wall I could live with (I have at least one that thin) - but for a regular use gun - I'd be concerned about it getting dented so easily. There is no margin to have any work done on the barrels short of sleeving or replacement. Such a gun should be towards the bottom of any price range because frankly, its near the end of its natural life.
Sleeving is fairly expensive - and reduces the value, especially where one of a pair is sleeved because the paired balance will almost certainly be lost.
New barrels are prohibitively expensive except for a top grade gun with (lots of) sentimental value! (My view)
As others have said, the guns will have been made in Birmingham by one of the makers who supplied retailers, very likely W & C Scott/Webley & Scott, or possibly Midland Gun Co. - both good makers.
