Nice piece with a bit of age to it. Is the hilt made out of bone? Ivory? Plastic/Bakelite/celluloid? Could help to narrow down the age. Just a guess for me would be a gambler's dirk/boot knife. These small daggers were used by 'soiled doves', gamblers, cowboys, etc. They typically had bone or MOP handles, often with simple line decorations like yours, many with fancy wavy blades. They date c. 1860's-1900 or so...IF it is what I'm guessing, that is.
