Tudor's introduction of the Oysterdate Chronograph in 1970 marked the beginning of a remarkable chapter in the brand's history. The manually wound Homeplate and Monte Carlo models established a distinctive identity for Tudor's chronographs, combining colourful dials with practical features and robust Oyster cases. In 1976, the arrival of the third-generation chronographs represented an important technical evolution. The new 9400 series introduced the automatic Valjoux 7750 movement, replacing the manually wound calibres of the earlier models and bringing with it a three-register dial layout and quick-set date. Accommodating the automatic winding mechanism required a considerably thicker case, giving rise to the affectionate collector nickname 'Big Block'. The design would remain a cornerstone of Tudor's chronograph collection for the following two decades, evolving into the 79100 series in 1989.

Dating to 1995, this Tudor Chrono-Time ref. 79170 belongs to the final generation of Big Block chronographs, produced shortly before the introduction of the slimmer Prince Date chronographs in the mid-1990s. Its 40mm stainless steel Oyster case retains the substantial proportions that define the series, while the bidirectional rotating bezel features a black acrylic insert graduated for 12 hours, allowing the wearer to track a second time zone. The silver panda dial is complemented by three contrasting black registers, a date aperture at three o'clock and the characteristic arched 'Automatic Chrono Time' signature. Powered by the automatic Valjoux 7750, the watch combines the recognisable design language of Tudor's early chronographs with the convenience of a self-winding movement. As one of the last Big Block references, the 79170 represents an important transitional chapter in Tudor's chronograph history.