By the beginning of the 1990s, the once state-of-the-art technology behind Patek Philippe electronic master clocks began to become obsolete and Patek replaced the systems with another first: the Telequartz. This microprocessor-controlled radio clock was 60 times smaller than tower systems. It still read the DCF-77 radio signal and displayed the time fully automatically via LCD while controlling countless subsidiary clocks without issue. During the 1960s, 1970s and early 80s, Patek Philippe made master timing clocks for Rolex and other leading watch makers such as IWC and Zodiac. Rolex used the Patek Philippe timing systems to operate small, synchronized clocks that were on the workbenches of watchmakers. Rolex watchmakers used these clocks to test the timing accuracy of the watches they were making. All clocks were housed in the company’s iconic green casing. More information :https://collectability.com/learn/the-worlds-largest-collection-of-patek-philippe-electronic-clocks/