The large yataghan blade is 556 mm long and has unstopped fullers.

George Moller, American Military Shoulder Arms, Volume III, states that in early 1861 the State of Massachusetts had 1500 Model 1841 Rifles fitted with saber bayonet lugs and bayonets by Ames Manufacturing Company of Chicopee, Massachusetts.  This alteration only consisted of brazing a bayonet stud with guide key (~25 mm) to the right side of the barrel 3.5 inches behind the muzzle. The state also purchased 900 saber bayonets from Ames. It is assumed that Massachusetts already had at least 600 saber bayonets on hand or could procure them from the government or some other source, to equip the remaining 600 rifles.  Massachusetts sold 1,000 of these rifles with bayonets to the State of Maine on August 21, 1861.

It is not certain that this bayonet fits the rifle in question.  It was made by Ames in the correct time frame.  It has the right muzzle ring diameter.  The lug and guide slot are very close to observed lug and guide on the rifles.  Plus the serial # fits into the range of produced rifles.  But until the bayonet is test fitted to the rifle it is pure speculation.

Clearly 900 of these bayonets would have been made by Ames and would have a typical Ames style brass hilt with a smooth rib finish.  The muzzle ring inside diameter would be about 22.8 mm and the guide slot would be about 25 mm long.  But what about the remaining 600?  Were all 1500 of the rifles modified with the same lug and key or were 600 rifles modified for another bayonet?  Could it be an error in the records and all 1500 were the same?