Looks to me like a slightly earlier (I'd date it to around the first quarter of the 1900s, but not being able to handle it, I'd just be guessing) version of what we today call a "rig hatchet" (which was purpose-designed for fitting joints of wooden drill derricks).
I can't see from just the one side-view photo, but the shape of the blade strongly resembles a broad-hatchet (small version of a more common broadaxe) I've got: sharpens to a chisel edge on one side only, to be used for squaring logs, joints, etc (for hewing and shaping, as opposed to chopping or felling).
My hatchet lacks the hammer face, which is what makes me assume yours is designed for a much more specific purpose than is mine.
Grandpa was a rig builder, back in the days of wooden oil derricks. He and his brother learned their trade doing ground support in the TN/VA coal mines, in the 1920s.
