I have come across a Purdey percusion double rifle, 16 bore. Built 175 years ago. I do not yet have pix and have not had it in my hands, so going on hearsay. Mechanically is is said to be very good, in ready to shoot condition. Bore seems excellent. Stock is solid, no cracks. External cosmetics reflect considerable pitting on the outside of the barrel and especially on trigger guard. I have made three different offers which are apparently the high offers. Knowing there are not many originals around and likely to be no more. The owner claims it is worth at least $5k. I am skeptical that it is worth even half that given the cosmetics. Oh. the right hammer screw has been replaced. What say you? How does one establish a value with so few comps available. Thanks.