Found this hammer head labeled a "3" on one side and the other shows "ATH" then a horseshoe symbol.  Also "made in USA" on same side.
Should I put a handle on this?
I wonder who made it.

Thanks
Bill

It is made by Atha, which was later bought out by stanley. The Horseshoe mark was put on almost all of their tools. There are a couple different marks using the horseshoe.

Not a blacksmith hammer, originally would have been called a stone cutters hammer. Used in the process of cutting stone into blocks for buildings, foundations, etc.

Probably could be used in some blacksmithing techniques, maybe as a cutter. Not good to forge with, wrong size/shape of face to do any moving of hot metal.

I see these all the time marked as "blacksmith hammer" at antique malls and such. Mostly be people who have no idea what it is, so "blacksmith hammer" gets applied to many odd hammer shapes.

This certainly is a stone mason's hammer.  It looks like what's called a trimming hammer.
I wouldn't consider using it as a cutter -- a sure way to damage the face, and probably the
face of the hammer you would strike with.  These are hard faced hammers for working
stone.

You can forge with it, especially if you round the face a bit and use for fullering.  Hmong and Mien
blacksmiths use hammers only a little different -- a little wider at both the pein and face.  Their work
is quite good, actually, and these folks make all the tools they need for farming, building, and
clearing forests -- axes, adzes, bill hooks, knives, and and all the tools they use for smithing too.

thanks guys!   How old is this? 

Atha sold out to Stanley in 1913 as I recall.  I think Stanley continued to use the Atha markings for a while, but then moved to Atha Stanley, and finally just Stanley.  I have a 2# engineers hammer marked Atha, but I don't think it was made prior to 1914. 

Scott or Aunt Phil will probably have the info.

This is from the stanley-atha era (40's)