Essentially a series of 'slaves' driven by regular electric impulses were connected in series with the master clock thus ensuring all clocks in a building were set to precisely the same time. It was an important development for factories, public buildings and railway stations.
So many of these have been stripped out and discarded across the years that early models are genuinely rare.
Judging by the case design the master clock seen at the October 9 collective sale conducted by Golding Young in Grantham dated from the second quarter of the 20th century. Instructions to the 2ft 4in (71cm) high glazed mahogany case read: To advance or retard the clocks set the indicator to the number of minutes required and press down the appropriate lever.
Proof of the increasing interest surrounding electrical clocks this example, estimated at £400-800, sold to a collector for £3400.
The buyer's premium was 17.5%.