Tudor Oysterdate "Big Block"

The Big Block owes its nickname to the case itself, thickened to roughly 14.5 mm to make room for the rotor of the self-winding Valjoux 7750. Launched in 1976, this vintage Tudor Oysterdate chronograph was the first automatic chronograph in the Tudor and Rolex stable, and in 1989 the family was renewed as the 79100 series, produced until 1995. Reference 79170 is the version of that series fitted with a black graduated 12-hour bi-directional rotating bezel, which sets the tone of the 40 mm steel case.

This example belongs to the 1990s, the later part of the run. The dial is black with applied baton indices and matching hands, while the 7750 arranges its three registers at twelve, six and nine and places the date at three, read beneath a cyclops in the acrylic crystal. A screw-down crown secures the case, and the watch is presented on its steel Oyster bracelet with a brushed folding clasp carrying the Tudor name.

The luminous plots and the hands have aged together to a warm cream tone, the kind of even colour that gives a Big Block of this period its character. The edge of the bezel insert shows minor scuffing. The bracelet links carry light surface marks and hairlines from years of use, with faint handling marks on the case flanks and case back. It comes with its original box.

For anyone looking at the vintage Tudor chronograph market, reference 79170 sits at the point where the Big Block formula had matured, still with the thick 7750 case and acrylic crystal that define the family.