A later 1973 Gents Master Clock
This is a fairly late example as it was built around 1973, having gone into service at an electricity sub station near Ipswich. The BST sign in the door reverses to show GMT when British Summer Time is no longer operating.
Gone are the architecturally pleasing cases of early models, being replaced now with this rather 'boxy' looking case.
The pendulum rod is a flat bar of Invar, a metal that shows far less expansion due to temperature changes than does steel. The bob is just a lead filled steel cylinder painted black.
The rheostat that you can see is for varying the current through the magnet's reset coils. This is needed because the slave clocks, like the Synchronome system, are all wired in series with the clock. As the current will vary each time a new slave clock is added, a rheostat is needed to adjust the current back to its correct level.
The cord hanging down with a ring in the end is to operate the advance and retard mechanism.