The Tudor “Big Block”

From Tudor’s illustrious back catalog, the three-register chronographs have until recently been (unfairly) viewed as the forgotten watches, the unsung heroes… but I would argue that they are among the brand’s most innovative and exciting watches!

The “Big Blocks” were Tudor’s third series of chronographs. The first Big Blocks were launched in 1976 and there were a number of obvious aesthetic differences to previous chronographs. The most striking detail was the introduction of a third chronograph register on the dial — an hour indicator. This was made possible by Tudor’s adoption of a new movement — the Valjoux 7750 —which was modified by Tudor to ensure it met the brand’s high expectations. The Valjoux 7750 also had a quick-set date function, which saved a lot of time when setting the watch up after a period of not wearing it. (We’ve all had the “joy” of adjusting a “slow-set” date!) The biggest development, however, was the introduction of an automatic movement, making these watches the first self-winding chronographs from the Wilsdorf group, over a decade before Rolex introduced its first automatic Daytona chronograph. This was a real coup for Tudor as it put the brand at the forefront of Swiss chronograph manufacture. It was this new advancement that led to the watches’ nickname. The presence of the self-winding mechanism and rotor meant that the watch case needed to be very deep, which resulted in the collectors’ term “Big Block”.

The first Big Block watches were the 9400 series. The 9400 consisted of three different references that were distinguished by three different bezel variations:

  • 9420 with acrylic tachymeter bezel (as per the refs. 7031 and 7149 previously);
  • 9421 with 12-hour calibrated bi-directional bezel;
  • 9430 with steel tachymeter bezel.

The Big Blocks were listed in Rolex catalogs as Oysterdates, but the very earliest dials only featured the words “Chrono Time” or “Automatic – Chrono Time” in an arc over the bottom chronograph register.


1989 Big Block


Ref. 79170

Following the colorful “Homeplate” and “Monte Carlo” dials in the first two series of chronographs, the introduction of the Big Blocks heralded a more understated “Daytona-esque” dial; most commonly either black with silver/white subdials or vice versa. These dials featured applied hour markers, with beveled/sloping ends. The date aperture had a painted window around it and the chrono registers had a raised inner section which gave the dial a three-dimensional quality. This dial version endured throughout the entire near 20-year run of the Big Block. There were also exotic-dialed 9000-series Big Blocks (also referred to as “Big Block Monte Carlos”).

In the late 1980s, Tudor replaced the 94300 series watches with the 79100 series, which kept the same Big Block case. By the time the 79100 Big Block was released, the dials all featured the words “Oysterdate” and “Automatic – Chrono Time”. Later 79100-series dials had straight (non-sloping) applied hour markers and the painted window around the date aperture disappeared.

Again, there were three references which were all differentiated by their bezel types:

  • 79160 with black plastic tachymeter bezel;
  • 79170 with black graduated 12-hour bi-directional bezel;
  • 79180 with steel tachymeter bezel.
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