In 1877, a German engineer, Kurt Siegel, founded a manufacturing plant in St. Petersburg for the production of machines, appliances, and accessories for the water and gas industries. Examples included bathroom fixtures, gas lighting, plumbing, laundry equipment, and so on. After the Bolshevik Revolution in 1917, the entire Soviet industrial infrastructure was nationalized, and the Siegel factory became known simply as “Hydraulics” (Гидравлика).

 

In 1946, the plant began developing electric timepieces and was again renamed to reflect its new profile: Electric Timepieces Leningrad (ЭЧЛ). The impetus for this change was the post-war importation of precision mechanical timing devices from the German company Strasser & Rohde. These timepieces were likely shipped to the USSR as finished assembly kits, with minimal manufacture and/or fine-tuning required.

 

From 1946–1966, the plant produced a large range of electro-mechanical clocks which were installed atop high-rise buildings in Moscow and Warsaw, throughout the Kremlin Palace, and in schools, factories, metro stations, and other public areas. Later, the factory’s focus broadened to include multifunction chronometric devices and other precision measurement instruments. These devices, meant to measure time more precisely than any other, were used in navigation systems and in nuclear power plants.

 

Meanwhile, during the 1950s, Electric Timepieces Leningrad was also participating in a side project of assembling mechanical watches made from parts manufactured at other factories. This began with partnerships at Uglich and Penza Watch Factories and the production of Zvezda wristwatches for women. These ЭЧЛ-assembled Zvezdas are distinguishable from their Uglich and Penza counterparts only by the tiny inscription at the bottom of the dial, which reads ЭЧЛ Ленинград.

In the 1960s and 1970s, Electric Timepieces Leningrad formed an even-closer partnership with the Petrodvorets Watch Factory. Beginning in the early-1960s, Petrodvorets provided ЭЧЛ with complete movements and parts for a new line of mechanical wristwatches. All components for these watches were manufactured at Petrodvorets Watch Factory; only final assembly took place at Electric Timepieces Leningrad. These ЭЧЛ/Petrodvorets hybrid watches were branded Svet (Свет, meaning "light"), and were identical to their Raketa counterparts, save for the printing on the dial. Notably, Svet watches made during this time bore the factory logo on the dial: a pentagon with ЭЧЛ stamped inside.

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In 1975, Electric Timepieces Leningrad was formally renamed “Chronotron” (Хронотрон). Svet watches continued to be produced for a number of years thereafter, but as a result of the factory name change, subsequently manufactured watches were produced without the pentagon ЭЧЛ logo on the dial.

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Since the 1980s, Chronotron has continued to manufacture precise timekeeping devices in all forms for use in public spaces, various facilities, spacecraft, and strategic weapons control systems. The factory is still in operation today.  

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(Sources: 1, 2, 3, 4)