Ball-peen (also spelled pein and pane[ hammer, also known as a machinist's hammer, is a type of peening hammer used in metalworking. It is distinguished from a point-peen hammer or chisel-peen hammer by having a hemispherical head. Though the process of peening has become rarer in metal fabrication, the ball-peen hammer remains useful for many tasks, such as striking punches and chisels.
The original function of the hammer was to peen riveted or welded material, which makes it as flexible as the surrounding metal. Today, the ball end of the hammer is used to cut gaskets, expand and shape the free end of copper roves, light rivets, and "set" rivets (which completes the joint).
I was fascinated with the handle; it's is a beautiful piece of work in and of itself. I feel sure this had a lot of use. The patina is striking on the whole hammer, it certainly got my attention. The handle is 12-3/4" long with an art deco look to it. The metal top is 4-3/4" long and both show some wear.