Bought this at garage sale 1dollar. Don't know what it is exactly.

It looks like a brick splitter to me. Providing it is 6 to 10 " long. If it is bigger then it's a big something else ... Mattock?

Although it may be a two bladed masonry/rock/brick hammer, it is may be a sheet metal hammer.   By flipping the hammer over the tin seams and creases could be worked without turning the work piece.

 

Looks like a sheet metal hammer to me as well. Would be great for texturing. 

With a long enough handle, that would also make a great backscratcher.

its a tomahawk chipping hammer for welding .