Watches with a power-reserve indicator
References in the Grail Atlas catalog carrying the power-reserve complication.
A power-reserve indicator shows how much wind remains in the mainspring — typically as a sub-dial sector arc with a hand sweeping from "full" to "empty." The complication originated on marine chronometers, where it mattered, and migrated to wristwatches as both a useful and a decorative feature. It is most useful on hand-wound watches and on automatics with long reserves (5+ days), where users want to know whether to top up before the watch stops.
What to look for
The Patek Philippe Calatrava 5235 and Aquanaut 5650G (Advanced Research) feature power reserves; the A. Lange & Söhne Lange 1 carries it as a defining design element. Panerai's Luminor Marina 8 Days (PAM 510, PAM 590) puts the indicator on the back, since the dial is a single open expanse — a different design choice. IWC's Portugieser Automatic 7-Day uses a long reserve and indicates it discreetly. Decide whether you want a dial-side or caseback indicator, and whether the reserve length matters to you (a 60-hour reserve indicator is mostly decorative; an 8-day reserve indicator earns its keep).
