SHARPS & HANKINS CARBINE QUESTION

I have a Sharps & Hankins Carbine in a strange configuration. It is a early gun ( Firing pin on on hammer )with a Navy type 24'' barrel. There is no leather on the barrel. The leather retaining screw holes have been filled and the front has been dove tailed in ( I think the original Navy type front band site was reformer and dove tailed in the barrel ) SERIAL NUMBERS -- Tang #726 Frame #726 Trigger Guard lever # 156 Barrel #926 Barrel Lever #926 Now this is the interesting part -- There is a Deep struck NUMBER THREE ( 3 ) on All Major Parts ( This is a period stamp Not New !! )Barrel, Barrel Lever, Frame,Trigger Guard Lever, & Hammer. I think the gun started out as a Sharps & Hankins Navy Rifle then went back to the factory and converted to a carbine or Existing parts were used to fill a Army carbine order. I would appreciate you thoughts in this matter -- Thank You