Synchronome Pictorial Guide

Pictorial Guides to Synchronome Movements, Cases and latches

Dating clues : The movement : Case styles : Case latches

A beginners guide to the features and age of your synchronome

How old is my Synchronome?

The company did not date the individual clocks and accurate dating is usually impossible. An approximate date can be derived from case and movement features, and from serial numbers by interpolation between the few numbers where there is external evidence of the date of supply such as an original invoice.

This is a "Work in progress" and I welcome any serial number where there is external evidence of the date of supply

Serial Numbers

The serial number on a Synchronome clock is stamped into the bottom of the Advance/retard plate (the NRA plate) on the lower left side of the A frame. A few early clocks had the serial on a Synchronome label

During the life of the company, ie up to around 1982, several different series of numbers were used. The gurus say that there were five different series but that two were predominant.

First Series

Synchronome started to put serial numbers on their clocks in 1908. This first series ran from 1908 until about 1962.

Second Series

The second series started in around 1962 with the introduction of the mark II movement.

So far as the minor series are concerned there is little firm information and several apparent anomalies even in those numbers which are known.

Coventry Series

A number of movements were marked with a "C" in addition to the serial number. It is thought that these movements were supplied by a firm in Coventry.

The clocks so numbered are not part of the main range of serial numbers, but form a separate series with dates between 1932 and 1938 (so far as I know at present).


For a quick check when offered a "bargain" remember:

The movement remained virtually unchanged from 1908 to 1962 (see movement details below) but minor variations are:

The early clocks did not have anything to prevent overthrow of the gravity arm but a buffer was fitted to all clocks from circa 1926

Up to circa 1930, the A frame was a fairly roughly finished casting and was painted with a black paint, often quite dull, almost matt, in appearance. Later clocks have a better finish to the casting and black crackle finish.

In the spark suppression circuit, wire wound resistors were used up to the 30's and carbon resistors thereafter.

The coil of the electromagnet which resets the gravity arm was wound with green coloured silk insulated wire in early clocks. Later clocks have a winding of enamel insulated wire finished with a wrapping of a black material. One source suggested that the changeover was circa 1934 but my records show at least some green wound coils up to 1950. No doubt there was a period when coils of both types would have been in stock.

The Mark II movement was introduced circa 1962

Most Mark II movements were fitted in the new style case in which the movement is offset from the centre of the case, but some mark II movements were fitted in cases of the earlier "round corner" style.

Most (all?) mark II movements have large white wirewound resistors made by Bulgin.

Some coils in the Mark II movements have a wrapping of a pale brown colour instead of black. I also have a picture of one with enamelled wire (mid brown) which has no wrapping.

Case styles also provide useful clues (see details below):

The Movement

Early days

Synchronome started producing clocks in 1900. In the first few years the clocks were of differing styles and movements and had no serial numbers.

The "A" frame movement

serial 954

In 1908 the company produced the now famous "A" frame movement and from that time on all genuine Synchronome clocks were given a serial number.

There were some minor variations in the movement of early models, for example early clocks had a slightly different form of latch for the gravity arm and had no buffer to limit the travel of the gravity arm.

The Double "A" frame movement

serial 107

Round about 1919 the company produced a modified design with what might be called a "double A" frame but the movement was apparently hard to adjust and maintain and only about 100 were produced.

A separate series of serial numbers was used for these clocks.
Synchronome supplied castings and parts

no serial

During the 1930s the company made castings and parts for the Synchronome available to enthusiasts. Clocks built from such kits or parts are often found and are frequently finished to a high standard. They can be distinguished from a factory built Synchronome because they have no serial number on the NRA plate.

The Mark II movement

serial 1162

The Mark II movement and case was introduced around 1962. It strongly resembles the earlier movement but has been modified for ease of manufacture with most parts now assembled from stamped brass held together by nuts, bolts and spacers.

At the same time a new case was introduced with the movement offset, but Mark II movements can also be found in cases of the earlier style.

Case Styles

type 1

The Architectural style

Synchronome started to use the Architectural style of pediment (a rooftop appearance) in 1900.

At that time they were producing an early form of movement.

In 1908 the countwheel escapement came into production using the typical A shaped backplate. the use of serial numbers commenced from the introduction of this model, probably starting from "1" since the remains of clock serial 15 are known. The architectural style case continued in use until circa 1919.

Note the carved detail in the top corners of the door. The door is inset into the case, not overlapping the front as in later clocks and though not visible in the picture the bottom of the case has a shaped bracket affixed.

No other details of this clock available, unfortunately, the picture just found its way into my computer.

type 2

The False Pediment style

In 1919 the false pediment is found, that is a flat top with a triangle shape mounted on top of the case so that from the front it resembles the architectural style.

The picture shows one of the earliest of the false pediment models with elaborate mouldings to the projecting top and bottom portions of the case and the door inset into the case.

Chris B. provided the picture and holds the copyright. The clock shown is Serial Number 876, The dial is a restoration from a photocopy of the original.

There may well be a slightly later models with simplified mouldings, though I understand that Synchronome did not themselves manufacture the cases (or the movements?) so the differing types of false pediment may just be versions from two subcontractors.

I have heard it said that the use of a false pediment ceased circa 1922 (serial 954 is known to have a false pediment).

type 3

The Flat Top style

From 1922 to 1948 a flat top style was adopted. Here again there are one or more variations with slightly different mouldings and possibly different door latches.

Thanks to Kim Bowers who provided the picture and holds the copyright. The clock shown has on the NRA plate "F.P. 340" which I cannot equate with any standard numbering scheme.

type 4

The "Round Corner" style

After the war, in about 1948, a case with rounded corners was introduced and this continued in use until the mark II movement was developed and for some time after that as several clocks with type 4 cases and Mark II movements are known.

The clock shown has an oak case, serial 4956, with anodised dial, black finish to windings.

type 4

The "Round Corner" style with bar below dial

This is a sub-style of type 4, the standard "round corner" model. I believe it occurs near the end of the series. As you can see it has a square dial and a bar across the door below the dial.


There is a variant of the type 4 case in which the door fits beneath the top of the case. The picture was provided by T.Y. and remains his copyright. Serial is C629

I am aware of another case style with metal case, possibly for Power Stations, and also some models having an all metal case, that is, no glass in the door. These latter were made for The London Underground.

All the above clocks, with the exception of the "coventry" series, had serial numbers in one continuous range. I do not know the highest number reached, but 6119 is thought to be one of the highest.

When the Mark II movement was introduced circa 1962 a new range of serial numbers was started, and a new Mark II case style introduced.

The round corner series of cases continued in production for some time alongside the Mark II cases so that three digit serials can be found in round corner cases. These indicate a Mark II movement.

type 4,power station

"Round Corner" sub style with black finish and Mark II movement.

The clock shown is serial 315. Copyright JH.
type 5

The Mark II style

Mark II movements (introduced in 1962?) were usually fitted in a wider case in a plain style with the movement offset from the centre line. Here again there are several minor differences in style. Clocks with no pilot dial are known and the clocks may have plain or black painted glass to the door. Occasionally a mark II movement was fitted in a round corner case (style 4)

Picture copyright Colin Reynolds. The clock shown is serial No.4306 It has a Westerstrand pilot dial (used by Synchronome when an alternate polarity (quiet) system was required).

A separate range of serial numbers was used for the Mark II. I do not yet know either the lowest or the highest serial in this new series.

Case Locks and Latches

Variations in case locks and latches can be noted but further investigation is needed before this helps with dating.

Up to the present, I know of five types:

1. Two locks

serial x03

The locks are fitted in the sides of the case.Two keyhole escutcheons in the side of the case are all that show externally. No latch.

2. Old style turn latch serial 954

2. Turn latches with "T" shaped handles, fitted to the front of the case (which has an inset door) The keep of the latch turns into a cast brass catch fitted to the edge of the case side. Two latches fitted to each case, no information about a lock

3. A latch with clamping action. serial C734 serial C734
The clamping lever is fitted to the front of the door, with the keep plate on the side of the ase.

4. The most common latch serial 4956

Hook and pin type latch. The "hook" is a swivelling arm fitted to the edge of the door which rotates into a pin fitment on the side of the case. Two such latches and one centrally placed lock are fitted to each case. This type was used for the vast majority of clock cases produced by Synchronome.

5. Clipover latch serial 4306

A latch similar to that used on brief cases etc.. The latch covers all screws when closed and tightens the door against the felt insert usually fitted to the case edges. Two latches are fitted to each case. Not sure if lock also fitted (someone will tell me)

Perhaps only used with Mark II cases (comment anyone?)

There are many other features which have changed as time passed, such as the pilot dial and pilot movement. Many pilot movements have their own serial number but these may well comprise several different series. Synchronome used outside suppliers for many of the pilot movements (and other parts) so the numbers on the pilot dial may have been issued by those suppliers.

I am not going to venture into these additional identification fields at present!

Part of Barrie's virtual Clock Museum