Don't know for sure, but it could be a tool for burnishing the cutting edge of a wood scraper. After filing the edge perfectly square, you run a hardened steel rod over it to deform it slightly and form a hook toward the flat face. I just use the shank of a drill bit, but I have seen screwdriver-like tools made for that purpose. Your gizmus looks like it would do that admirably. Scraper in a vise, thumbs press on the wings, use the right or left slot depending on which edge you want the hook on.