This is a custom-designed balisong, commonly known as a butterfly knife. The defining characteristic of this weapon is the fan-like opening of a freely pivoting blade, allowing rapid deployment or concealment. As a result, butterfly knives are outlawed in many countries. It has been given a forced patina using lemon and mustard dripped onto the surface.\n\nIf you think it's messy now, wait until you see it under a blacklight