Suzkat, yes that's a top swage, but it's not a hammer, the handle is so the person holding it, doesn't have his hands broken or burned. The smith strikes it with his hammer or power hammer. In the process it will get quite warm. Looks a bit big for a barrel swage, as most barrels are just finished round on the swage block, by rotating. The American Pioneer videos have good DVD's on barrel making.
Bill