This bayonet does not have a muzzle ring to fit over the associated firearms barrel.  It is designed to fit a double lug adapter that has been attached to the side of the firearm's barrel.  There are two rectangular extensions in the brass casting of the hilt, both having rectangular holes to accept the lugs on the firearm's adaptor.  One is found on the side of the pommel and the other is on the side of the cross guard.  A large exterior leaf spring, mounted in a recess milled into the side of the hilt, has a pin that protrudes into the extension on the pommel to lock the bayonet to the hilt.

This double lug adaptor was designed to provide a sword bayonet attachment to the various firearms found in personal use in the southern states at the out break of the US Civil War.  This included sporting rifles and shotguns, both single and double barreled, of multiple calibers or gauges.  This is the source of the popular term "Shotgun Bayonet". 

There are two other US brass hilted bayonets with a very similar construction, Reference #411 and Reference # 412.

Albert N. Hardin, The American Bayonet 1776/1964, #115, Type III

The yataghan blade is 22.125 inches (562 mm) long, 1.375 inches (35 mm) wide and .375 inch (9.5 mm) thick.  The 4 inches of the top edge of the blade nearest to the hilt flares out to form a wide and apparently purposeless surface.  The deep narrow fuller runs almost to the hilt.

The 4.625 inch (117 mm) long cast brass hilt is very similar to Type I (Reference #111) but not of the same mold.  The blade is in a reversed manner when compared to other yataghan sword bayonets of the time.  When the ture edge of the blade is down, the flat of the hilt is also down.

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Russ Pritchard & John Ashworth, Confederate & Southern Agent Marked Shotguns, Page 298, provides great pictures of this bayonet showing details of the spring and lug extensions. 

"The Memphis Novelty Works made all manner of brass castings and offered shotgun bayonets as proclaimed in their September 19, 1861 advertisement.  It is possible that the hilts of Types I (Reference #411) and III (this bayonet) were made by Memphis Novelty Works and blades attached were accured from Cook & Brother and other sub-contractors.  Based upon this theory, Types I and III are products of the Memphis Ordnance Department and later Briarfield Arsenal in Columbus, Mississippi"  Page 307