Abstract: An elongated transluscent plastic cylindrical member has a mechanical pencil formed at one end and has a longitudinally directed ridge projecting radially from the member on which are located first slide rule scales. A longitudinally slotted transluscent plastic tubular member slideably receives the cylindrical member with the ridge within the slot. The tubular member carries second slide rule scales along the slot for cooperation with the first scales. The cylindrical member carries a lamp and batteries for illuminating the scales.