With the Calibre 97, (originally introduced in 1997 at the World Presentation of Haute Horlogerie), Franck Muller is the fi rst watch brand to have perfected the bell chime in a wristwatch; a world premiere in the history of watch making. Preceding the production of this watch, the sound quality now heard in the Grande and Petite Sonnerie was only possible in a pocket watch. Originally, 18th century watchmakers used very ample shapes so as to leave the maximum amplitude for the sound, which escaped through elaborate cut-out designs in the casework. Franck Muller was able to successfully reproduce the sound in a wristwatch as a result of extensive research on complicated alloys and the creation of a bell that would fi t into a case no larger than 36.80 mm in diameter and 11.3 mm in height. Two hammers strike the inside of the bell, producing a high and low sound, which allows one to distinguish between the hours, quarters and minutes. The Grand Sonnerie, with a passing chime, announces the hours and quarters on the quarter and the Petite Sonnerie sounds the hours and quarters at the appropriate times. There is also a silence mechanism should the user not wish to hear the chimes. In addition, the Calibre 97 also has a minute repeater which makes it possibile to hear the hours, quarters and minutes upon request. On the dial, the user can see the renowned striking mechanism indicator patented by Franck Muller as well as a ?silent mode?, ?Petite Sonnerie? and ?Grande Sonnerie? indicator. The Calibre 97 also incorporates a third complication: the perpetual calendar in which the day of the week, date, month and retrograde monthly equation of time, the 24 hour counter, leap-years and moon phases. All of these features are visible on the dial.