Cal. JB7 (also called Cal. E or No. 300) is an alarm watch movement produced by Excelsior Park. It measured 36 mm (16 ligne) in diameter, though the circumferential gong increased this to 42 mm (24 ligne).
When used in a pocket watch, the crown was at 12 along with the 12 hour alarm set sub-dial and the hinge for the back of the case, with the small seconds hand at 6. It was also used in stationary applications including automobile dash clocks with the crown at 6 and sub-dials rotated 180º.
The design of the movement is highly unusual for Excelsior Park, with the balance bridge at 12 and 3/4 plate. But it does not resemble the products of the company’s subsidiary Magnenat-LeCoultre in Le Sentier: Their Le Risound repeater has a distinctive star-shaped bridge design, and they focused on repeaters rather than alarm watches. So it is likely that it was designed and produced in Saint-Imier or sourced from another firm.
