Omega sold many watches to the military forces during WW II among them the British. The Marine Forces used wristwatches with black dials while the Air Forces preferred white dials and center-seconds. On the dial the radium-coated symbol of the "broad arrow". Inside and outside the case back: the letters WWW the arrow and the numbers.A similar watch is published in "Militari da Polso" by L. Canetoli and F. Ferretti.