This particular regulator was used at the Royal Observatory, Cape of Good Hope from 1911. Until the advent of Shortt’s free pendulum clock system, the Riefler regulators were the best timekeepers available. It is interesting that these were never used in the Royal Observatory, Greenwich; this may have been due to patriotic reasons. Greenwich continued to use Dent 1906 as the sidereal standard until it was superseded by a copy of Riefler’s design, made by E.T. Cottingham, in 1922.

The movement, dial and pendulum are enclosed within a sealed copper tank with glass dome. The tank is designed to be partially evacuated, protecting against changes in the clock’s rate due to barometric variation. Fine regulation of the clock can also be achieved by adjusting the internal air pressure. The mechanical movement features Riefler’s escapement, which impulses the pendulum through the suspension block rather than the conventional crutch system. The escapement employs two co-axially mounted wheels that provide locking and impulse. The driving weight is re-cocked electrically by two coils that are situated on the left-hand side of the movement. The nominal twelve-inch regulator dial is signed ‘S. Riefler München, No. 152, DRPN 100870, 1905’ and has a viewing aperture for the electrical contacts, for transmitting electrical pulses to slave dials and other instrumentation.