Hi Steve, I believe that the Henry Parsons Patent for damascus chopper lump barrels is indeed No. 201 of 1868.All the examples that I have seen or read about are hammer guns with non-rebounding locks which would put them in that era.The extra cost of making damascus tubes with an integral lump and machining to fit when a lump of a better wearing steel could be brazed in place,quicker and cheaper,probably rendered the practice obsolete fairly quickly.

Better to keep your mouth shut and be thought stupid,than open it and confirm.