A Fine and Extremely Rare Gold and Ruby-Set Rectangular Jump Hour Wristwatch with Wandering Minutes, Vacheron Constantin, Genève, Movement No. 414384, Case No. 257150, circa 1932

18k, circular nickel finished lever movement, 18 jewels, bi-metallic compensation balance, precision regulator, 6 adjustments, silvered engine-turned dial, aperture for Arabic digital hour display, outer Arabic 60-minutes track, ring aperture for wandering minutes with triangular ruby-set minute hand, large rectangular case with enlarged bezel, snap back, case, dial and movement signed, with an 18k  pink gold Cartier deployant buckle. 

Lambelet & Coen, The World of Vacheron Constatin Geneve, p. 389, pl. 3189

Jump hour watches, sometimes referred to as digital watches, were a popular alternative to standard two-handed analogue watches during the 1920s and 1930s.

The watch movement is the same between the two styles, however on the jump hour examples, the hour hand is replaced by a disk with 12 hours on it. As the wandering minutes hand goes from 59 to 60, the hour jumps from one hour to the next, ergo the name.

Vacheron Constantin produced very few such examples at this time period. In the 1990s, the company would launch a model, the Saltarello, which would call upon the design of this and similar pieces from this time.