Abstract: A clock, called a "mystery" clock because of its almost totally transparent nature, comprising a transparent dial bearing reference markers (11), a minute indicator, transparent except in the area of a reading pointer (28') and an hour indicator, also transparent except in the area of a reading pointer (26'), indicators and dial having a common geometric axis (Y) and being carried by a frame or surround (20) and at least part of these indicators and dial having teeth at their periphery, masked by the surround (20), for driving them in rotation, in relation to the surround (20), about said axis (Y).