Abstract: An indicating device for a tank containing a valve having a head for opening and closing the valve that includes a body portion having a top end and spaced apart bottom end with a peripheral surface therebetween, and indicia means on the top end of the body portion. Gripping means on the peripheral surface is provided to facilitate mounting and removal of the body portion from the valve head. Enclosing means extends vertically in the body portion upwardly from the bottom end, with a cavity having a pair of vertically extending spaced apart cavity walls adapted to receive therebetween the valve head, such that vertical mounting and removal of the body portion on the valve head by the gripping means is obtainable. Retaining means is connected to at least one of the cavity walls for releasably securing by frictional engagement the body portion to the valve head thereby requiring a force for mounting and removal of the device from a valve head.