What is the value of a W Greener double barrel 12 gauge shotgun It does have the crossed axes and and British proof marks Number is 9215?

Is this a breech loader or muzzleloader? W. Greener muzzleloaders of the mid 1850s were engraved with the phrase "Indestructable by Gun Powder" They were elegant and light weight. A double in good condition should bring several thousand dollars. Out of my collection of several dozen antique guns, the W. Greener from 1856 is my favorite to shoot and hunt with. Of my collwction of shotguns that include Parkers, LC Smiths, etc., the old greener is the best ballanced/shouldering of the lot. email me photos of your Greener. james_moran@uml.edu