I am a flatware manufacturer of forty + years. This is a spoonmakers tiest, which would be set in a stump, and used to forge silver spoons. The crescent shapes are for swaging the ends of the handles. This is still done the same way where I work, and at Old Newbury Crafters in Amesbury Massachusetts. Trust me on this, mystery solved!
From the shape of the crescents, this is probably a nineteenth century pre-civil war tool. After that, the hand forging of spoons in America declined, and more industrial methods were adopted.