Rare 18ct Gold Breguet Pocket-Watch, French, Circa 1818

• Moon Dial - If we imagine life in the 17th century, the only source of ascertaining the time of day or night would have been the local church or municipal clock striking every quarter hour, and able to be heard by all in the village. In England, when longcase clocks became popular and more affordable in the late 17th century, the function of timekeeping and source of time was moved to within the home.
  
  An additional feature on some longcase clocks was to display the phases of the moon, that is the new moon, the full moon and the waning moon over the lunar 29 ½ day cycle. This information was important for farmers for working out cropping schedules; for travellers to know the amount of moonlight on a night they planned to travel; and for those who lived near the sea required knowledge of the tides.
  
  Where included, the moon dial is usually in the form of a disc incorporated into the main dial plate, usually in the arched top section. The lunar cycle starts with the new moon displaying, which is a dark night sky and no man-in-the-moon face being displayed, and then progresses to the full moon face showing on the 15th day of the lunar cycle, and back to no face displaying as the moon wanes. Most lunar dials are partially concealed on each side of their opening in the main dial plate by semi-circular "humps" that allow the painted face to emerge slowly just as the real moon goes out of and back into the earth's shadow.
  
  Nowadays, details of the lunar cycle is published in diaries, almanacs, and newspapers and although some modern longcase clocks are still manufactured with working moon dials, they are more for decoration than for use.
• Engine Turned - Engine turning is a decorative technique used on metal surfaces to create intricate curving or geometric pattern. The process involves cutting a series of lines into the surface of the metal using a rose engine or decoration lathe which rotates the metal as it cuts, allowing the operator to create a repeating pattern that covers the entire surface. The resulting surface has a shimmering, reflective quality that is often described as "engine turned." Where an engine turned item has been enamelled, the term used to describe the decoration is usually guilloche.
  
  Engine turning was originally developed to decorate metal objects such as firearms, scientific instruments, and other metal objects that required precise and elegant design.
• Pair Cased - A pair cased watch is one with a double case. The movement is encased, and for additional protection this is fitted into an outer case.
• Carat - A carat (abbreviated "ct") is a unit of measurement used to describe the weight of a diamond or other gemstone, and separately is a unit of measurement used to describe the weight of precious metals such as gold,.
  
  For gemstones, one carat is equal to 0.2 grams or 200 milligrams. The weight of a diamond is one of the Four Cs (along with cut, colour, and clarity) that are used to determine a diamond's value.
  
  It is important to note that a diamond's weight does not necessarily correspond to its size. A diamond's cut, which affects how well it reflects light, can make a diamond of a lower weight appear larger than a diamond of a higher weight. Additionally, the carat is not the only factor to determine the value of a diamond, other factors such as clarity, colour and cut are important too.
  
  In the gold industry, the purity of gold is measured in carats (abbreviated "ct"), with 24 karats being pure gold and lower carat numbers indicating a lower purity level. So, for example, 18 carat gold is 18/24 or 75% pure gold, and 12 carat gold is 12/24 or 50% pure gold.
• Duplex Escapement - A duplex escapement is used in clocks and watches to control the release of energy from the mainspring to the timekeeping mechanism. The duplex escapement is a variation of the lever escapement and is characterized by the use of two pallets, or escape wheels, to control the release of energy.
  
  In a duplex escapement, the balance wheel, which oscillates back and forth, alternately pushes against the two pallets. This allows the energy stored in the mainspring to be transferred to the balance wheel in a controlled manner, keeping the timekeeping mechanism accurate.
  
  One of the advantages of the duplex escapement is its relatively low friction, which helps to maintain accurate timekeeping and prolong the life of the clock or watch. Additionally, the duplex escapement is relatively easy to maintain and repair, making it a popular choice for clockmakers.
• Chapter Ring - A separate metal plate on the face of a clock, on which the numerals for the hours and sometimes parts of the hours, are displayed, usually wheel shaped and sitting on top of the dial plate. The chapter ring is often a feature of the clock and can be silvered or enamelled to stand as a contrast to its background. The hours are usually shown in Roman numerals, although in the late 19th and earlt 20th century, Arabic numerals became fashionable.
• Circa - A Latin term meaning 'about', often used in the antique trade to give an approximate date for the piece, usually considered to be five years on either side of the circa year. Thus, circa 1900 means the piece was made about 1900, probably between 1895 and 1905. The expression is sometimes abbreviated to c.1900.
• Movement - The technical name for the workings of a clock or watch, and does not include the dial or case.

This item has been included into following indexes:

• Breguet (brand) (Switzerland) - pocket watches and wrist watches 85
• pocket watches, case type - open face, gold / gold-plated case 1,381
• pocket watches, country - Swiss made 463
• pocket watches, features - repeater / repeating 107
• pocket watches, period - Georgian 289
• watches - pendant 106