There is quite a bit of information available on William Jackman Jeffery. He was at the address mentioned on your gun somewhere between 1890 and 1910. He had experience in the gun trade having worked for some noted London Gunmakers. He started his own business but never actually made a gun at all. He sourced all his stuff from the trade and turned it out as to customer requirements. I am fairly confident that the actual Maker of your gun would have been The Midland Gun Co. in Birmingham. I have one almost identical and from the same era but with damascus barrels. Yours, as was mine, was proofed for black powder. I have since had mine proofed for nitro. The 2 3/4" information is probably just engraved on the forend fastener on the barrel. I would suspect that the gun is made as a sort of general purpose pigeon/heavy game gun. I use mine quite a bit as a duck shooting gun.
I recently managed to source a correct case for the gun but it is a bit tatty.
All of the guns I have seen that bear the Jeffery name have been decent well made guns but of a wide variation in grade. My other Jeffery is a nice little 16 bore boxlock ejector. He is perhaps more famous for big game rifles and big game rounds that he was instrumental in developing such as the .600 Nitro Express and the .404 and .333 Jeffery.
I would suggest having it checked out to ascertain that it is still in proof and then go shoot it; but with black powder ammunition.
I would have queried Roy's valuation until yesterday when I went to the C.L.A. Game Fair at Belvoir Castle in England and saw some of the asking prices for various hammer guns.
The business of W.J.Jeffrey was bought out by Holland & Holland. I don't know how comlete their records are but you may be in luck. Lagopus.....
