Jaeger-LeCoultre Reversible Dual Time Wristwatch

• Date Aperture - A date aperture is a cut out section in the face of a watch or clock, displaying the day of the month.
• 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.
• Back Plate - On many types of clocks, the movement operates between two plates, usually made of brass, one at the back, and the other at the front, which forms a mount for the dial.
  
  On English bracket, mantle and table clocks the backplate was often visible through a glass door or panel from the late 17th century, and could be profusely engraved with scrolling decorations, flowers, foliage, birds, and figures. The engraving could also include the maker?s name.
  
  The amount of engraving reduced and became simpler as the 18th century progressed, and by 1800, had been reduced to a border, often with the maker's name in the centre. By the early 1800s all decoration had ceased, and only the maker's name was added, and by the Victorian era, most bracket, mantle and table clocks had no engraving.
• Movement - The technical name for the workings of a clock or watch, and does not include the dial or case.
• Subsidiary Dial - On a clock or watch, a subsidiary dial, also called an auxiliary dial, is a dial that is secondary to the main dial and may show seconds, day of the week or month, or strike silent. A subsidiary dial may be within our outside the main dial, and a clock or watch may have several subsidiary dials.
• Guilloche - A form of classical decoration consisting of a repeating ornament of interlacing curved bands, sometimes forming circles, and further decorated with rosettes or other flower forms.
  
  The name is derived from the inventor, French engineer Guillot, who invented a mechanical method of inscribing fine repeating patterns on to metallic surfaces.
  
  On enamelled items with guilloche decoration, the surface is firstly engraved with the repeating pattern, and then covered with several layers of enamel, each of which is fired.
  
  Where the item has not been enamelled the form of decoration is usually called "engine turned".

This item has been included into following indexes:

• Frederique Constant - wristwatches 86
• Jaeger LeCoultre (Switzerland) - Reverso / Duo / Duetto wristwatches 44