I would speculate that it may have been an early half hatchet which had the hammer poll ground down to a point, and was used for ice or stone and had one point of the cutting edge pounded or worn off. I'm guessing that its use has been modified from what was originally intended.. Back up at my ranch, I have some stone hammers that were used to square large blocks of limestone for building purposes, and they had notched cutting edges, but the way that the face is curved off, I'll still bet that it was square when it was new. Unless you happen to know who had the old farm/barn and they would know something of the history of the family, the real truth may be lost in history/mystery.