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AFAIK, "Anson & Deeley" were the British patent designers of the most commonly-made boxlock SxS double shotgun action used today - aka the generic Gold Standard for boxlocks.
There was also "Deeley & Hedge", "Greener", and some others, who experimented & made a differently-designed boxlock actions, in the 1800's & early 1900's, which eventually fell by the wayside - as every maker went over to the better A&D design.
A&D leased their several patents out to a multitude various gunmakers, too many more to list, for the actual manufacture.
Additionally, the two designers also each had their own design for the forend release/latch mechanism, one a pushbutton on the FE tip, the other a downward-pivoting latch in the middle of the FE wood.
A&D, did make a design model, and some complete guns around 1875 - Is that what you're looking at, or just a SxS stamped with "A&D" as a quality advertisement ?
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