They aren't too rare. If you spent less time trolling people here and more time looking around, you could find out for yourself.
Certain makers specialized in heavier type fowling & pigeon guns, so obviously guns bearing their names will have 2 3/4" chambers over makers who's specialty was making light game guns.
My G.E. Lewis is from 1905, original 2 3/4" chambers, it's odd that it's proofed for 1 1/8 oz instead of the more common 1 1/4 oz. My guess it was made for a fella who specialized in wood pigeon & shore bird gunning. The action is profusely engraved with wood pigeons, plover and golden plover.
Lots of Greeners, Rossons, Lewis, Jeffrey, Wild, even Purdey's , etc out there with original 2 3/4" chambers.
