Derby Swissonic Jump Hour Speedometer

Inventory Number: WW2109025LC

Made circa 1970, 40 X 35mm, 14K gold plated case, with ESA9176 quartz movement, operated by a 357 1,5V cell. 

Its technology uses a rotatory electronic system to read the time. The time can be read through the speedometer window where the digits are shown.

How does this watch work?

The Derby watch is considered to be the rarest and weird-looking jump hour watch ever. Despite space-age materials, the movement was not tested sufficiently before being launched to market. The battery activates an electromagnetic coil that operates a balance wheel with permanent ferrite magnets, the same way as in other Transistorized Electrics. The rotating roller jewel on the balance moves an escapement wheel which transfers torque to a long metal rod on the drum-machine filled with a row of Teflon-type gears. Corresponding gears move the seconds-drum which gradually rotates the first minute-drum every 60 seconds, then the second minute-drum every 10 minutes, and all of the drums including the hour-drum every 60 minutes. The jumping functionality is obtained by means of a tiny and delicate spring installed permanently on a light-blue wheel combined with the seconds-drum.

On loan from the private collection of Mr. IAO.