Stopwatch, Type A-8, Navigation Watch for Ground Speed 1942 "Jitterbug"
Here is an authentic WWII-era aircraft navigator's Watch, Navigation (Ground Speed) Stopwatch, Type A-8, made by Elgin to Air Corps US Army spec #94-27749. With a serial # AC42-670, indicating manufacturing year of 1942. Type A-8 stopwatches were used in any WWII aircraft with a navigator, such as heavy (B-17, B-24, B-29) and medium bombers (B-25, B-26) and large transports (C-46, C-47, C-54).
The outer ring of the dial counts up to 10 seconds and the inner dial located at the standard 12:00 position count up to 10 minutes of the 10-second revolutions. The A-8 was known as the ‘jitterbug’ because of the loud and fast ticking of the balance at 144,000 beats per hour. Yep, just try to hear that over the cacophony of multiple radial engines...
According to C.G. Sweeting’s book "Combat Flying Equipment":
The Type A-8 was a navigation stopwatch designed for timing ground speed meters for determining the velocity of aircraft relative to the ground. One revolution of the Type A-8 hand was equivalent to ten seconds. The dial was white on early Wittnauer Type A-8 watches and black on Waltham watches produced from 1940 onwards. Elgin produced a Type A-8, 15 jewel, black dial stopwatch under military specification no. 27749. Waltham, the Federal Television Corp. and Aristo Import Co. manufactured Type A-8 stopwatches under military specification MIL-W-6510 (specification published in August 1951 and superseded No. 94-27749A published in July 1945). Under MIL-W-6510, continuous running movements were required to have not less than 15 jewels and the non-continuous movements were required to have not less than 9 jewels.
After winding, one press of the crown starts the second hand in motion. As the hand passes 10 seconds, the small hand on the inner dial advances one mark on the scale and counts minutes. One revolution of the inner hand is 5 minutes, another revolution is 10 minutes. Another press of the crown stops the hands. Once wound, the Elgin A-8 continues to run until the mainspring is out of energy (in A-8's of other manufacturers, the mainspring would stop when the crown is pressed after running).
Our Elgin A-8 has definitely seen a bit of service. The engraving on the back is nearly completely worn off, but can be read with the right lighting (our attempts at photos could not capture the details of the engraving, but it is there and shows the spec # and serial #). It has a few small nicks from its service, but seems to run. Sometimes takes an extra press of the crown to get it started.