Power reserve indicator

A power reserve indicator (originally called Réserve de Marche) is a complication of the watch, which is designed to show the amount of remaining stored energy.

Power reserve indicators were employed very early on marine chronometers and later in the accurate Railroad grade pocket watches.

In 1948, Jaeger-LeCoultre introduced a power reserve indicator designed for production in a series of watches called the Powermatic which utilized the LeCoultre Caliber 481.

In general, the indication of the power reserve is sometimes represented through a needle or hand or it may be indicted by a revolving wheel viewed through an aperture.

The LeCoultre 481 utilized a differential device to show the power reserve stored in either a self-winding or hand-wound mainspring.

The power reserve is at the 6 position on this automatic watch. Here it is indicating that 25 out of 40 hours remain.