05-29-2023-1335 - The U.S. Naval Observatory has maintained a Time Service Department since 1880. At right are a pair of Reifler precision pendulum clocks, photographed in their underground vault c. 1910.

https://www.cnmoc.usff.navy.mil/

 

The U.S. Naval Observatory has maintained a Time Service Department since 1880.  At right are a pair of Reifler precision pendulum clocks, photographed in their underground vault c. 1910. 

https://www.cnmoc.usff.navy.mil/Our-Commands/United-States-Naval-Observatory/Precise-Time-Department/