Silver-cased verge pocket watch (outer case missing)

Record summary

Held and catalogued by British Museum (object number 2018,8001.36), this is a calendar watch by Michael Johnson, made in London (England), dated c. 1700. The Atlas places it in the Early Modern Horology period (1600 – 1750) of its Pocket Watches collection. Materials and techniques recorded by the source: brass, steel, silver, glass. Recorded dimensions: Diameter: 51 millimetres Height: 66 millimetres (inc pendant) Depth: 31 millimetres. The record is illustrated with 4 photographs.

Assembled from the source record's structured fields. Dates and attributions are given as the source states them; where a field is missing the Atlas leaves it blank rather than estimating.

Catalogue description

Atlas type guide

Calendar, moon-phase and perpetual calendar watches

Calendar complications range from a simple date to the perpetual calendar, which automatically allows for months of different lengths and leap years until 2100. Pocket watches with perpetual calendars were made in the eighteenth and nineteenth centuries; Patek Philippe made the first perpetual calendar wristwatch in 1925, and series production followed in 1941. The annual calendar (Patek Philippe, 1996) needs correction only once a year.

Moon-phase displays use a disc with two moons and 59 teeth advanced daily, approximating the 29.5-day lunation; more precise trains reduce the error to one day in over a century.

General guidance written by the Atlas editors about this kind of object. It is not a statement about this particular piece; for that, rely on the source record above and on physical examination.