GPO impulse (slave) wall clock No. 4a with George VI cypher, dated 1952

This large and impressive wall clock, designed for use in GPO offices and exchanges, did not have its own power source but operated on an electrical impulse generated every 30 seconds by a master clock - hence the term ‘slave’. The master clock would be wired to a number of slave clocks, ensuring accuracy and consistency across the network.

The clock features a very substantial octagonal bakelite case, moulded by H E Ashdown Limited of Birmingham, which was introduced in 1949 superseding the earlier round wooden cases. The clock is very heavy, with an enamelled steel dial weighing 700g secured to an 800g steel falseplate mounted in the 1.5kg case. The clock also has 1/8 inch (3mm) flat glass, a painted spun brass sight ring and counterbalanced aluminium hands.

This example is dated May 1952. The mottled red-brown bakelite case is in excellent condition with no damage. The dial is also near perfect, with a few slight blemishes most notably next to the 12 (visible in the photos). The glass is clear and unmarked. The original pulse movement (which could not operate without a master clock or other pulse generator) has been replaced with a high quality German UTS quartz movement. The hands are original to the clock and have been re-colleted to fit the arbors of the new movement.

The clock has been fully disassembled, cleaned and sensitively restored as appropriate. It is supplied in outstanding overall condition and full working order (it  takes a single AA battery).

Dial diameter 12 inches (305mm); width across flats 430mm; depth 82mm. Weight 3.7kg

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