According to the Archives of Universal, the present piece with gilt calibre 19 movement with autocompensating Breguet spring, black dial, indication 5 to 60 hm, seconds 360 graduation on 30 sec, turning bezel with luminated hand, marked at 6 Universal Genève, A. Cairelli Roma, was manufactured in 1939 and sold to A. Cairelli Roma, Military Air Forces
Used by bombardier airplanes operator during WWII, the present tool is an exotic and rare find highlighted by its remarkable condition, highly unusual for a war tool. The crown operates the start/reverse/reset functions. The button stops the hand in its track. The hand makes one revolution of the dial every 30 seconds. The luminous numerals indicate the distance travelled by a dropped bomb in hm (hectometer: 100 meters). The operator, knowing the launch altitude, would set the arrow at the corresponding distance. Then, he would use the crown to start the timer, and press the button once the hand reached the desired distance to stop it. When the bomb is dropped, one more push on the crown would set the hand in motion counterclockwise, thus starting the countdown to the moment the bomb would reach the ground. At this point, another push on the button would stop the timer, and a last activation of the crown would reset the hand.
This model is illustrated in Universal Watch Genève Chronographs and Complicated Wristwatches by Pietro Giuliano Sala, pp 471