Even a novice could identify these faults without having to involve a "double rifle expert". Its not rocket science! Contrary to what certain American gun-writers would have us believe, there is nothing 'magical' or 'super-natural' about Brit doubles.

I dunno what circles you travel in, 500grains, but around here most Brit doubles are fairly valuable and are consequently well looked-after. The two most-stuffed double rifles I have personally seen in the last decade were a Chapuis 9.3 and a Ferlach .458. SxS shotguns are a different story, though!