Cal. 42 is an oblong 12×13 ligne chronograph movement produced by Excelsior Park for Gallet and Zenith in the 1930s and 1940s. It is a hand-winding movement with 30 or 45 minute counters at 3:00 on the dial.
The shape is highly unusual and is different from other movements in Excelsior Park’s Cal. 4 family. It measures 27.10 mm at its narrowest and 29.40 mm at its widest, being “taller” in the case than it is across. This shape was achieved by reducing the width of the main plate all around (most other Cal. 4 movements measure 14 ligne or 31.60 mm diameter) but more along the sides where less components were located. The height of the movement could not be reduced to 12 ligne because of the location of the balance and wheel train. Although most watches that used this movement had traditional round cases, a fair number had oval cases to match.
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 |