Albert Hardin, "The American Bayonet 1776 - 1964", describes the associated firearm as a smoothbore .67 caliber flintlock musket converted to percussion.  The three bands, trigger guard, trigger and straight butt plate are all of brass.  The small lock plate is marked "H. E. Leman / Lancaster, Pa."  The unique and complex bayonet stud is fastened to the right side of the barrel near the muzzle.  Most probably the stud was created when the arm was converted from flint. 

There is very little information on this musket.  When, where and how many were made is unknown.

Bayonet Variations