Cal. JB15 is an 18-19 ligne chronograph movement produced by Excelsior Park (Jeanneret-Brehm) since the 1930s. It was an advanced movement with fine components and was anti-magnetic. The movement stop/start/reset is controlled by a button co-axial with the crown. Some examples include a sliding lever to stop the hands during operation (hacking). The movement was variously listed as 18, 18.5, and 19 ligne in diameter. A 24 ligne version was also offered.
Cal. JB15 is fitted with a Jeanneret family signature feature: A compartment in the movement holds a collection of spare parts including a balance wheel and jewels.
A rattrapante version of Cal. JB15 was also produced. It featured a pushbutton 1 hour counter-clockwise from the crown (typically at 11) to operate the flyback hand.
The movement is seen in a 1931 advertisement and is listed then as “Nouveau chronographe”, suggesting recent introduction. It still appears in the Excelsior Park catalog in 1950.
Cals. JB1, JB11, and JB15 include the Jeanneret spare parts compartment embedded in the movement next to the balance. This was patented in the 1920s. The parts container included the following text in various languages:
- Dutch: “Hieronder reservedeelen”
- English: “Spare parts in here”
- French: “Ci-dessous fournitures de rechange
- German: “Hier ūnten Ersatzstücke”
- Romanian: “edesubt piese de schimb”
See Also: Patent CH100230A