Scarce P1840 Constabulary Carbin Bayonet with Scabbard. Its not too clear but it looks like there might be a WD with arrow mark on the scabbard which would make this a post 1856 manufactured item. Note also that the bayonet spring is missing and it looks like this was period removed. The bayonet spring was usually removed during the Crimean war for the Land Transport Corp, thus making this a very interesting item. 
Dimensions : OA 422mm Bl 335mm Sl 78mm Mrd 20mm Sm 40mm Bw 24.8mm