It is not a good idea to let a watch run out of power reserve before recharging it. In principle, the following applies the tighter the spring, the smoother the gait. A power reserve indicator, which tells the wearer when the watch needs to be rewound, is correspondingly useful. Power reserve displays were initially built into precision timepieces such as marine chronometers or railroader’s pocket watches.
After the Breguet brand had already presented a corresponding wristwatch prototype in 1933, Jaeger-LeCoultre made the power reserve display available to a broad audience in 1948: The world’s first series wristwatch displayed the spring tension was called the Powermatic.
The watch manufacturers introduced the power reserve display because customers in the late 1940s mistrusted self-winding, i.e., a watch with an automatic movement. They feared that their watch would still stop at some point. The solution was to display the mainspring’s tension on the dial permanently.
The power reserve disc, visible through a cut-out on the dial, was printed by Jaeger-LeCoultre with the number of hours and thus provided exact information about the remaining power. Since then, the power reserve indicator has often been built into watches with an automatic movement, although it can be dispensed there.
The Power Reserve Display – A Function For All Price Ranges
A power reserve display is not only reserved for watches like Rolex GMT with manufacturing movements. The function can already be found in timepieces. Standard works by Eta and Sellita are used here. The Seiko Presage automatic with power reserve display even offers a manufacture caliber – the 4R57 – with a decentralized display showing the remaining power of more than 40 hours. But the power reserve display rarely enjoys the undivided attention of its wearer. The simplest variant is the combination with a small second.