The Savage 220D is the last of this hammerless series of shotguns. There are 6 basic M220 single shot hammerless shotguns, not to be confused with the current production 220 bolt action rifled slug gun. First Model Utica, Second Model Utica, 220A, 220B, 220C, and finally the D model. Basically, the internal action parts on the C and D suffix models are the same. The serrations on the top of the barrel over the chamber are not as wide and long as previous models, and an external screw was added mid way to the forearm. I hope this helps.