The developer of this navigation watch was the lieutenant commander for the United State Navy P.V.H Weems.
In 1929, Navy Captain Phillip Van Horn Weems
in conjunction with Longines (and Wittnauer) developed the Weems
Second-Setting Watch for nautical navigation. Given the turbulent cockpits and the thick gloves needed for altitude flying, the Weems was typically oversized.
The second-setting watch owning to the low gear ratio between the hour and minute hands as compared with the second hand of an ordinary causes, no provision is made for setting the second hand of an ordinary watch. This means that the watch set to the correct hour and minute may still be in error as much as 30 seconds, which, near the equator, represents an error in longitude of 7.5 miles. The second-setting watch was devised to permit the exact second to be set, thus avoiding the correction ordinarily required by the navigation watch. This is done in the standard model by rotating an inner seconds dial. The hour and minute hands are set in the usual way. When the minute hand is properly set, it should of course be exactly at a minute division when the second hand is at 60.
Pilots could listen to the time signals from the Radio.Time.Signals.
from 5 minutes before each hour to the hour, the silence after 50th
seconds of the fifth minute indicates at once the number of minutes of signal yet to be sent. The rotating inner dial displayed the correct minutes and graphically showed the margin of error from the original set time.
Air navigation by: Weems, Philip Van Horn, Published in 1943 pages 299 to 304