Longines-Wittnauer Weems Second-Setting Watch Sidereal Model

Before 1927, watches used with sextants for celestial sightings could only be set to the minute. A watch error of 30 seconds caused a navigational error of up to 12 kilometers (7 miles).

In 1927, P. V. H. Weems devised a watch with an adjustable second hand that could be set using radio time signals. These examples were his personal navigation watches.