Patented in 1918 by Svante Elis Strömgren and Jens Olsen, the present watch is timed for sidereal and mean time, intended primarily for use at sea and much less costly than a ship's chronometer.
It is thought that only three other examples of such a watch are known to exist to date, one of which is extensively described in "Klassik Uhren", 1/1995, pp. 56 -65.
Professor Dr. Svante Elis Strömgren (1870-1947), Swedish/Danish astronomer, was the director of the astronomical observatory in Copenhagen and in 1926 the chairman of the International Astronomical Association.
Jens Olsen (1872-1945), Danish clockmaker, locksmith and astromechanic, was during five years the head of the Royal Instrument Maker Cornelius Knudsen in Copenhagen until establishing his own workshop as astromechanic and watchmaker in Hallingsgrade. He made the famous "World Clock" with 12 movements in Copenhagen's Town Hall, inaugurated by King Frederik IX in 1955 (see "Klassik Uhren", 1/1995), p. 58).