The year 1963 was a big one for watch lovers: two of the most important chronographs ever made suddenly appeared, each with design choices that would change wristwatches forever. These were the Rolex Daytona and its iconic tachymeter bezel, and the very first Carrera, which introduced a totally new case shape with faceted lugs that became a Heuer signature. While we have already done an in-depth report on the original Carrera reference 2447, this three-register chrono was quickly followed by the reference 3647, which shared the same astoundingly legible dial, this time only with two sub-registers.
Original documentation shows a steep price difference between these two chronographs: $69.50 for the 3647 versus $89.50 for the 2447. Obviously, the 3647 shares many traits with its older sibling, including the same dial-manufacturer (Singer, also trusted by Rolex), the famed Carrera case, and the metallic rehaut which also acted as an internal tension ring to improve water resistance. Similarly, the early examples like the one pictured above exhibit only a “Swiss” mention on the dial, while later examples would read “T-Swiss” to comply with a legal requirement for labeling tritium dial watches. For these early pieces, you should also expect the original crown to be unsigned.
The Carrera 3647 was produced until 1969and eventually replaced by the reference 7753, which came with a major change. The original chronograph movement, the Valjoux 92, was replaced by the Valjoux 7730, which changed the minute counter from 45 minutes to 30 minutes. Stylistically, you’ll notice a lot of other differences, like a thicker handset and indexes, characteristic of the fashion at the end of the 1960s (the same style can be observed on contemporary Breitling Top Time models, for instance). As with any later Carrera, the winding crown should have the Heuer logo.
It is fascinating to see how little the Carrera changed within the first decade when it still came in its ground-breaking round case. The true rupture in design happened in the late 1960s when the C-shape case was introduced alongside the in-house automatic caliber 11, and eventually expanded to the manually-wound Carrera, which still relied on Valjoux-sourced movement (7733/7734 for the two-register configuration, 7736 for the additional hour counter). It clearly shows how revolutionary and influential some simple components like a round case with peculiar lugs and a functional tension rings had in the design of the Carrera, up to this day.