Launched in the 1976, the Tudor Big Block was the third series of chronographs that the Swiss brand had introduced to their catalog. Surviving for two generations with the 9400 series that was launched in 1976 and the 79100 series that debuted in 1989 and produced until the Big Block’s discontinuation in 1996, it was a large step away from the chronographs that preceded it. Evolving from Tudor’s second series of chronographs, the Big Block featured a host of innovations that modernized the watch. To begin, the Big Block featured a new movement the Valjoux cal. 7750. Not only did this change the dial design from the twin-register designs of the two previous chronograph series to a triple-register design to accommodate a new hours subdial, it also allowed for the introduction of a quick-set date feature at 3 o’clock too. However, it didn’t stop there, the Valjoux cal. 7750 also provided a rather practical benefit over the two previous chronograph generations, it is automatic rather than manual-wind like what came before it. However, to accommodate for the presence of the self-winding rotor and complicated date function, the watch case had to be made a little deeper, which resulted in the collectors’ term “Big Block”, which this third chronograph series is still affectionately known by. With several dial variants like silver panda and black reverse panda along with different bezel materials such as steel, black acrylic tachymeter, or the black acrylic graduated 12-hour bi-directional bezel like on the ref. 79170 that we have here, the Big Block Chrono-Time, as it was named by Tudor, has plenty of options to choose from.

Watch is in excellent overall condition. Case shows some surface wear, and a few dings visible along the edge of the lugs as well as near the lug holes. The turning bezel insert is excellent and does not show any significant scratches or marks. The original silver dial has oxidized with a light purple hue. The coloring is generally even with the exception of a small area along the edge of the dial between 5 and 6 o'clock. Watch comes with 11 links total, 1 of which is removable. The bracelet shows light stretch and fits a 7 1/4" wrist.

Retaining vintage elements like its acrylic bezel insert and hollow center links, the ref. 79170 and its fellow third-generation chronograph references acted as transitional models in sorts as they combined these features with modern Valjoux movements and robust dimensions.