Yes. And I have observed on older guns send back to the factory for later work, that the "horns" on the hammers were removed by the factory.

Brian, What do you guess was the use for the lugs on the back of the early hammers?

I would suspect that Dean's statement is a best guess of mine as well.

They must have figure more mass meant more reliable operation. But late deemed as not needed. The change came after the multiple cost cutting improvements/changes of the 19-teens. So I suppose that Hayes was reaponsable for the hammer change.