Cal. JB4 is a round 14 ligne chronograph movement produced by Excelsior Park from 1928 through the 1960s. It is a hand-winding movement with 30 or 45 minute counters at 3:00 on the dial. The movement measures 31.60 mm in diameter and served as the base for a family of movements used by many watchmakers.
All Excelsior Park Cal. JB4 family movements are instantly recognizable thanks to the distinctive U-shaped cock that supports the chronograph wheels. Nearly every other chronograph uses a Y- or wishbone shaped cock or bridge. The overall design of the movement is also “reversed” from many other chronographs, with the rabbit-shaped hammer falling on the crown side and a counter-clockwise balance cock. Although not a finely-finished movement, it is high in specification with a Breguet spiral hairspring, screwed balance, and machined springs. The chronograph minutes recorder is equipped with a “sautoir” (jumping mechanism).
One version, Cal. JB4-24h includes two novel features: A central 24 hour hand used for orienteering and a “seconds corrector”, allowing manual adjustment of the running seconds hand using a crown at 9:00.
Excelsior Park chronograph movements were used by Gallet, Zenith, and Girard-Perregaux as well as in-house by Excelsior Park and Moeris. These were roughly similar apart from their finishing and the specification of a mobile stud carrier by some brands. The “JB” stands for Jeanneret-Brehm, the name of the founder of the Excelsior Park factory.
| Complications | Notes | |
|---|---|---|
| Cal. JB4 | Chronograph minute counter | Base movement |
| Cal. JB4-68 | Cal. 4 base | Movable hairspring stud |
| Cal. JB4-24h | Cal. 4 base; 45 minutes, 24 hour hand | |
| Cal. JB40 | Chronograph 45 minutes, 12 hours | |
| Cal. JB40-68 | Cal. 40 base | Movable hairspring stud |
| Cal. JB42 | Chronograph 45 minutes | Oval 12×13 ligne |