J. W. Benson Monopusher Chronograph Pocket Watch
Inventory Number: PW2112005
Made circa 1950 in London, by J. W. Benson, 51mm, nickel silver openface case, white enamel dial, 24-hour makers, 30-minute counter at 12 o’clock, the tachymeter ranges from 15 to 300 km/h. The dial has four indication scales in different colors (black, blue, red, and green) to display different ranges of speed. By looking at the four-color zones on 30-minutes counters, users can easily determine the perspective speed range and observe readings indicated by chronograph second hand.
Marked Depose Argentan (registered Nickel silver) on the caseback, with Valjoux 5 KVM caliber, 17 jewels. Valjoux Cal. 5 KVM is a pocket watch column-wheel chronograph movement. Introduced around 1912, it was produced through 1975.
Functions: hours, minutes, small seconds, tachymeter, and 30-minutes chronograph counter.
The most common use of a tachymeter is for measuring the approximate speed of a vehicle over a known distance. Based on how many seconds it takes a vehicle to travel 1km or 1 mile, the average speed within the distance can be calculated.
1) Start the chronograph when the vehicles commence travel.
2) After the vehicle has traveled 1 km/1mile, stop the chronograph. The approximate average speed within the distance can be determined by observing the present position of the second hand and reading the outer bezel.
About J.W. Benson
J.W. Benson was one of the most respected watchmakers in London during the second half of the 19th Century and was one of very few early wristwatch houses that were English. J. W. Benson was the official supplier to many exalted clients, it is official watchmaker to the Admiralty, and held a number of Warrants, being watchmakers to Queen Victoria, the Prince of Wales, the Tsar of Russia, and several other royal families.
In 1889 the company took over the firm of Hunt & Roskell and continued successfully until WWII when their factory was bombed. In 1892, J. W. Benson became a limited company. The firm of J. W. Benson Ltd continued until 1973 at which time the name was sold to the then Royal jewelers, Garrard & Co. Ltd.