This is a close up of the 14EB movement. In focus is the balance jewel and it’s golden colour shock spring. Shock springs come in many different shapes and allow the mechanism to resist knocks and harsh movements without damaging or breaking the balance shaft.

The purple circle is a jewel and is the item referred to when movements have “17 jewels”. These jewels used to be made from natural materials such as diamond, sapphire, ruby and garnet. Such material is quite cost prohibitive and in 1902 a process was developed to produce synthetic sapphire and ruby.

These sorts of materials are used as they have a very low and predictable friction, good temperature stability and can operate without lubricants. For comparison the static coefficient of friction of brass-on-steel is 0.35, while that of sapphire-on-steel is 0.10–0.15. Sapphire surfaces are super hard and very durable and can maintain smoothness over decades of usage.

In the US during World War 2 jewels were actually requested to be set aside as a reserve for the fulfillment of present and future defense orders, and such other orders and uses as may be authorized from time to time by the War Production Board. As such a useful tool to coordinate, calculate and cooperate en mass – accurate and hardy watches were required.

Typically a watch needs no more than 17 jewels –  two cap jewels, two pivot jewels and an impulse jewel for the balance wheel, two pivot jewels and two pallet jewels for the pallet fork, and two pivot jewels each for the escape, fourth, third, and center wheels. In more quality watches, to reduce any positional errors, capstones were added to the lever and escape wheel bearings, making 21 jewels in total. However it is not unusual for high end automatic movements to have 30 jewels.

There are diminishing returns when adding more jewels than necessary – more jewels in a watch does not equate to a higher accuracy or a longer operating life. If you consider marine chronometers produced by Longines, Waltham and Thomas Mercer – these are incredibly accurate and rarely exceed  21 jewels.

This did not stop manufactures inflating the number of jewels in movements to the point of completely pointless endeavors such as the Orient or Waltham 100 jewel watch. When the consumer was presented between choices of more or less jewels it was obvious what they would choose. “V6 or V8 sir?” 

As with most excess an organisation stood in and mediated this behaviour. The International Organisation for Standardisation (ISO) and the organisation Normes de l’industrie Hologère Suisse (NIHS) published a new standard in 1974 – ISO 1112. This basically prohibited manufacturers from including pointless jewels in any advertising. 

With modern quartz watches the time is measured by the quartz crystal and electronic circuits – this can lead to no jewels being present and sometimes leads to the 0-jewels label.