A detection system according to the present invention includes a control device detecting fraud performed in a game table by using a result of an image analysis performed by an image analyzing device, and 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 (121) is included at least in the middle, and white layers (122) or thin-color layers (may be layers having a color thinner than that of the coloring layer (121); not illustrated in the drawing) are stacked on both sides of the coloring layer (121) disposed in the middle. A multi-layer structure, in which a coloring layer (121) is included, and white layers (122) or thin-color layers (while not illustrated in the drawing, the layers may be layers of a color that is thinner than that of the coloring layer (121)) are stacked on both sides of the coloring layer (121) of this middle, is employed.