J. Sewill Brass Deck Watch with Duplex Movement

• 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.
• Fusee - The fusee movement was used in clocks and pocket watches from the mid 17th century. The fusee is a cone shaped drum within the works that is linked to the barrel of the spring, usually by a length of chain.
  
  As the mainspring loses its tension over time, the cone shaped barrel compensates for this by increasing the tension, by pulling the mainspring tighter, thus ensuring the time remains constant.
  
  Use of the fusee in clocks was superseded by the "going barrel" in the mid 19th century and for pocket watches at the beginning of the 19th century.
  
  The fusee continued to be used in marine chronometers until the 1970s.

This item has been included into following indexes:

• chronometers and deck watches - marine 88