A mekugi nuki is a tool for removing the mekugi (peg) from the handle of a sword so the sword can be disassembled.  This one is worn around the neck and is handy at sword or gun shows.  The metal is brass and the wood is lignum vitae (densest of all hardwoods).  About 3 3/4″ (9.5 cm) long.

New, of course.  $25.