After sinking of Titanic, Radio Act 1912 was enacted, requiring 24 hour watches at sea. This led to clocks of such design. Ship radio operators had to maintain "silent periods" when they would not transmit, instead listening for distress calls. Silent periods are denoted by blue and red coloured sectors on clock dial. Dial depicts 1-12 on outer, 13-24 on inner ring, with 4x3 minute radio silent zones (in blue & red). Chromed case, clock, circa 1950, has a hinged, pressure fit glazed bezel and a back plate with 4 screw holes. Clock approximately 7 inches in diameter, height approximately 3.5 inches. This is a rare collectible! (Ps : Clock does not wind well. Can only do very short winding. Repair is recommended).