Development of the marine chronometer advanced substantially in the eighteenth century making it possible for large strides to be made in the watchmaking world.
The development of the marine chronometer was driven by the need of sailors for a precise measurement of time so they could accurately determine longitude.
John Harrison in the 1730s further perfected the marine chronometer. These days a certificate is issued as proof that the watch is a chronometer in accordance to ISO standards.
Lunar PhasesMinute Repeater