The jewels themselves aren't of great value, so the number of jewels in the movement need not bear any relation to the functional value of the watch. Jewels in a watch have been incorporated since the beginning of ‘time’, and it would be surprising for an uninformed person, that these jewels are actually used to increase the efficiency of a watch rather than for show.

Especially the jewels are used in watches as rubies, sapphires, garnets and diamonds. To mount the watches into the escapement is a time consuming, painstakingly detailed procedure because the jewels have to be firmly set into place by screws so small that you need special equipment to do so. Earlier the jewels were either from stones that were too small or had too many flaws to be used in jewelry.

There are number of jewels in a watch, a regular lever watch generally has 7 jewels; two each for the upper and lower balance pivots, one for the impulse roller, and the remaining two for the pallets. During the 1950s a jewel fashion came into existence, about 75-100 jewels are being used per watch. However, this had nothing to do with increasing the efficiency of a watch.

In late 1800s, real rubies and sapphires were used in each watch, and these metals were extracted from the natural resources in impure forms. In the scientific century, scientists came up with a method for artificially creating synthetic rubies and sapphires. This made it easier on the watch industry. More over watch makers created synthetic jewels out of these natural impurities.

There was no policy regarding the use of jewels until late seventies; anything could be used anywhere. Then, the ISO came up with standard definitions for the kinds of jewels used in watches and played a vital role in watch making. This definition clearly differentiates between a functional and nonfunctional jewel. Thus a functional jewel is defined as a "jewel that serves to stabilize friction and to reduce the wear rate of contacting surfaces of the components of a timekeeping instrument", while a nonfunctional jewel is one that is used for ornamentation.

Now the watch industry had a source of stones that not only was cheap and plentiful, but was of a far higher purity and without the mechanical flaws found in naturally-occurring stones. Jewels which are technically functional according to the ISO standard, but which are used in places which serve no effective purpose other than to increase the jewel count of a watch. We will look at some examples of these later.