A resonance chronometer is a rare complication.
The resonance chronometer consists of two largely independent watch movements which are coupled only by a common balance staff and by their resonance: If the half-cycle of one balance wheel slows, the other is accelerated - and vice versa. The distance between the two balances is only half a millimeter.
Harry Winston realized this principle, which F. P. Journe had first adapted for the wristwatch, in 2001 in the series model Opus One. Around the same time Journe also offered this specialty for watch connoisseurs within his own model range: the F. P. Journe Chronomètre à Résonance.