Jump Hour Watches

Movement & mechanism

• A twelve-position hour disc advanced by a jumper spring that is tensioned throughout the hour and released instantaneously at its end
• Minutes typically still shown conventionally by a hand or a separate disc
• Requires more precise energy management than a simple continuously-rotating hour hand, to achieve a clean instantaneous jump

Identification

• An aperture (rather than a hand) displaying the hour numeral
• A distinctly 'digital' looking dial layout despite being fully mechanical

Terminology

• Jumper spring — the mechanism storing and then releasing energy to snap the hour disc forward instantaneously
• Digital display (mechanical) — a jump-hour or similar aperture-based display, as opposed to hands

Known variations

• Single jump hour (hour only)
• Jump hour combined with jumping minutes ('digital' style)

Pocket-watch ancestry

Jump hour (and jump/wandering hour) mechanisms were devised for pocket watches in the late nineteenth century; their most celebrated wristwatch expressions came during the Art Deco period, directly adapting the earlier pocket-watch jumper mechanism.

Collecting notes

Art Deco-era jump hour wristwatches are a distinct and stylistically celebrated collecting niche, valued for their design as much as their mechanism.