Extremely accurate time-keeping would make it possible for a ship to find its exact position at sea, and the government offered big rewards for this purpose. Harrison, Mudge and Arnold are the three most famous names in this connection and their painstaking labors did much to ensure the supremacy of British shipping and the worldwide fame of British clock making.

The earliest clocks were almost certainly made by blacksmiths; they had heavy iron frames and they show few signs of the small-scale precision associated with the work of a true clockmaker. With the advent of the portable clock came the widespread use of brass, and the accuracy and neatness typical of such mechanisms. By the middle of the eighteenth century few households were without a clock of some type; usually a long case or grandfather.

The demand for these grew so great that the trade became divided into a number of specialists, each of whom made one or more parts. A country clockmaker ordered his requirements, assembled them and added his name on the front of the face. The majority of surviving clocks made in country towns and villages were put together in this manner, and only occasionally were they made entirely by the men whose names appear boldly on them.

The first clock cases were of gilt metal or brass, and the familiar type known as the lantern clock is a typical example. Wooden cases were introduced in the seventeenth century, mostly of oak veneered with ebony but later with walnut and other woods. Inlays of floral marquetry and later of satinwood and ebony stringing followed fashions that prevailed at the times of manufacture. Whereas a good Tompion will realize a thousand pounds or more, clocks by less exalted makers can be bought comparatively cheaply.

An important factor is the condition of the movement; of greater interest to the collector than the case. Continual use during the centuries will have caused wear and necessitated replacement of parts; if this has not been done with great care and by a knowledgeable craftsman much of the value will have been lost, and it will be found that it is a very expensive matter to correct it.

An apparently fine clock will sometimes disclose on examination that the entire striking mechanism has been removed, or that the old escapement has been changed for a more modern, but less capricious, one. Further, movements have been adapted to fit cases, and vice versa; a long case of small size, known as a grandmother, should be treated with great caution. Old examples do exist but are very rare, and unscrupulous fakers have manufactured the majority of them.

In France, clocks were placed in large and ornamental cases, sometimes with matching wall-brackets, covered in tortoiseshell inlaid with brass (Boulle work). The fashion lasted from about 1690, through the eighteenth century and later. In the early 1700's cases began to be veneered with kingwood, tulipwood, and other rare woods, mounted in ormolu and designed in styles to match those prevailing for furniture. Other clocks were given cases of ormolu and bronze, sometimes set with Dresden and other china groups and with Sevres porcelain flowers. Genuine specimens are rare and expensive, and they have been copied carefully and often. A feature of an old French clock movement is that the pendulum is suspended on a silk thread, which can be lengthened or shortened to regulate the time.

German clocks often resemble closely the French. Others had movements of which the framing was of wood instead of the usual brass.

Clocks in their present as well as in their old forms came in different shapes and sizes and designs as well. Clocks were placed in large and ornamental cases in France. Clocks came in different ornaments made of different metals like iron, sliver, woods, bronze, etc.