A detection system including a control device detecting fraud performed in a game table by using a result of an image analysis performed by an image analyzing device. A substitute currency for gaming used for this detection system has a multi-layer structure in which a plurality of plastic layers having different colors are stacked, a coloring layer is included at least in the middle, and white layers or thin-color layers (may be layers having a color thinner than that of the coloring layer; not illustrated in the drawing) are stacked on both sides of the coloring layer disposed in the middle.