The chart above is a rough and ready guide to what date you can attribute to your Synchronome. The records of serial numbers no longer exist, so there are several attempts by owners to catalogue numbers from eBay adverts and else where on the web, in the hope of getting an accurate dating chart.
The production most likely varied each year, and also a clock bought in 1923 may well have been made in 1922, or even 1921 maybe. Also production during the war years would have been affected for obvious reasons.
This list does not cover numbers that are prefixed or suffixed with the letter 'C' There were approximately 800 of these built in the 1930's in, it is thought, Coventry, hence the letter 'C'.
Original Synchronome Literature and Instructions