Riefler escapement
![Riefler escapement used in the Clemens Riefler regulator clock, 1893. Shows the bearer (A'), knife edges (c), agate support surfaces (P), suspension spring (i), locking escape wheel (h), impulse escape wheel (H), and pallets (S,S').](/Images/godic/202502/07/Riefler_escapement_drawing2010.png")
![The Riefler precision pendulum clock No. 549, currently (2006) serving as the workshop regulator in the horological workshop of the Deutsches Museum.](/Images/godic/202502/07/Rief549-Deutsches_Museum-Dial2010.JPG")
![Side view, closeup of double escape wheel of Riefler No.549. This clock has clear synthetic ruby pallets. (Dial on the right side.)](/Images/godic/202502/07/Escapement_of_RiefNo549-19292011.JPG")
![Riefler clock, NIST museum, Gaithersburg, Maryland, USA. 54 inches (134 cm) tall. This clock served as the first US time standard, from 1904 to 1929.](/Images/godic/202502/07/Riefler_clock_NIST2011.jpg")
The Riefler escapement is a mechanical escapement for precision pendulum clocks invented and patented by German instrument maker Sigmund Riefler in 1889. It was used in the astronomical regulator clocks made by his German firm Clemens Riefler from 1890 to 1965, which were perhaps the most accurate all-mechanical pendulum clocks made.