This is the matching bayonet for the P-1841 Smooth-Bored Brunswick Rifle
The British Brunswick Rifle with back action lock was officially adopted in 1837 with a 36" barrel incorporating two groove rifling for a belted ball. Trials continued to experiment with multiple grooved rifling and eventually, in 1841, a smooth-bore version was experimentally developed. In effect an inane trial in that the whole point of the adoption of the Brunswick was the increased accuracy of a rifled barrel. (Conceivably these trials were for comparison purposes for accuracy and rate of fire.) The “manufactured” smooth Brunswicks were soon abandoned and now are only a footnote to military firearms history.