isxs, note that Purdey bought-in and retailed a number of "graded" guns that were Birmingham made. Most/all makers did similar marketing. Purdeys made their best work guns (mostly) in-house. Some made their "graded" guns in-house and bought-in best work guns. "Gun Trade" meant that guns, parts, workers, contracts, patents, house secrets, etc. all got swapped/sold/bought around as somebody had a chance to make money.

DDA