639 - A VERY RARE WWII ROC OPERATIONS ROOM ELECTRIC SLAVE ‘SECTOR’ WALL TIMEPIECE

A VERY RARE WWII ROC OPERATIONS ROOM ELECTRIC SLAVE ‘SECTOR’ WALL TIMEPIECE SMITHS ENGLISH CLOCK SYSTEMS GPO SYNCHRONOME, LONDON, DATED 1944 The brass-framed slave mechanism incorporating a solenoid driving a pivoted arm fitted with a pawl to advance a ratchet wheel set beneath an angled bridge by one increment every thirty seconds, the frontplate stamped with serail number 032272 and the bridge inscribed SYNCHRONOME PATENTED, the 18 inch circular cream silk screen printed dial with an inner track annotated with vertically aligned Arabic hour numerals 13-24 followed by principal chapter ring annotated with conforming larger twelve-hour numerals divided by doubled-up triangular panels spanning 2.5 minute intervals coloured in a repeating sequence of yellow, blue and red, the circumference with further minute track incorporating Arabic five minutes, with black painted steel moon hands set behind a hinged spun oxidised brass bezel incorporating a canted silvered insert to interior, applied to a turned moulded mahogany surround stamped NO 6 and EHR 44/1 to verso and applied with two horizontal batons incorporating a metal hanging eye to the upper. 56cm (22ins) diameter, 6.5cm (2.5ins) deep. Please note that the catalogue footnotes below were updated 29/08/2026 to include the provenance to Lt Col Bob Gardner and revisions to the last two paragraphs. Provenance: The property of a professional sportsman and commentator. Previously in the collection of Lt Col Bob Gardner author of A History of Clocks in the RAF. The ‘sector’ or ‘colour change’ clock was developed after 1918 by Major General Ashmore to assist ground control operations in the tracking aircraft in real time. The system worked by logging the position of a sighting on a large grip map using a series of coded counters grouped within a metal block stand. The first counter would be matched to the corresponding colour of the triangle of the sector indicated by the timepiece at the time of sighting by the Royal Observer Corps. The other counters were a mixture of number and letter codes to designate the nature of the aircraft (aircraft type, height, number of aircraft, hostile or allied and designated track). As the additional sightings and/or radar detections came through the frames containing the counters were moved along the by operators using magnetic rakes. In addition to the counters within the ‘block’ stands other symbols would be placed on the map to indicate the direction (arrows for heading or discs in the event of the aircrafts circling) which again were colour-coded to the corresponding triangle of the sector clock at the time of sighting. This system allowed ‘Fighter Controllers’ to ascertain at a glance the progress and heading of each formation and thus undertake strategic decisions as to when to scramble intercepts if required. The colour coding was crucial as allowed a very complicated and rapidly evolving picture to be seen in timed groupings thus allowing RAF interceptor squadrons to remain on the ground until necessary. This saved significant amounts of time and fuel hence fighter aircraft could then stay in the air for longer periods when required. Due to the of the speed of incoming enemy raiders speed of response was critical, hence the RAF had to be prepared to scramble at a moment’s notice. The earlier sector clocks incorporated coloured segments spanning five-minute intervals. However, due to the increased speed and increased volumes of raids it was deemed that five-minute periods were too long for effective tracking, hence the divisions were halved to 2.5 minute intervals during the latter part of WWII. The GPO collaborated with the Magneta Clock Company to supply sector slave dials with bifurcated inward-pointing sector markings (to facilitate the 2.5 minute colour change), however present lot belongs to another group fitted with movements supplied by Smiths English Clock Systems with smaller individually coloured sectors. These examples would have probably been used in tandem with a Synchronome electric master timepiece (a modified version of a model 6A). The master timepiece would send a pulse every thirty-seconds causing the solenoid to advance the mechanism of the present lot by that amount twice a minute. The advantage of this system is that many slave dials can be connected to an accurately rated master timepiece. Another almost identical slave timepiece, also with a Synchronome movement, was sold at McTears, Glasgow sale of Air Land & Sea: Militaria & Ethnographica 19th July 2023 (lot 155) for £3,000 hammer. The lack of RAF crest to the centre of the dial of the present lot indicates that it was destined for use by the Royal Observer Corps (ROC). The 'FHR' initials to the rear of the wooden surround indicate that the timepiece was at the GPO Factory, Holloway, London. Condition Report: Please note the condition report was updated alongside the catalogue description 29/08/2026. The vend