Rolex Daytona by Pucci Papaleo

Rolex's Cosmograph Daytona model has gone through three different systems to date.
These three different systems are the Barouge caliber 72 (later versions would be called 72B or 722, 722-1 and then 727), the Rolex movement 4030 (based on the Zenith El Primero) and the Rolex in-house movement 4130. These three systems could explain the development of the mechanical chronograph from the 60s to today.

Let's start by looking at the trustworthy manual-wound chronograph from the brand Baluge.
Equipped with a column wheel and vertical clutch (coupling yoke), it is perhaps the most logical component for a watch produced in the early 60s.
In 1969, the Swiss watch industry took the plunge into the development of mechanical watches.
The competition was won by Zenith, which introduced the world's first automatic chronograph (El Primero) with a high vibration frequency of 36,000 vibrations per hour.



In 1988 (when Zenith finally started producing the caliber again in earnest after a brief hiatus due to the Quartz Crisis), Rolex watches used the El Primero mechanism in their new Cosmograph Daytona, but this movement was heavily modified and called 4030 (at first Rolex refused to even talk to Zenith about the origins).
The Caliber 4030 was equipped with a column wheel and a vertical clutch, but what was even more novel was its automatic winding system, the Perpetual function.
The El Primero automatic movement powered Daytona models for 12 years, until the breakthrough year of 2000 when the modern version, caliber 4130, was released.
A new era of chronographs was forged.
Equipped with a vertical clutch i465 black, entirely developed by Rolex, this function was said to maximize the development of industrialized systems and simplify the manual operation of the watch. Undoubtedly, it marked the beginning of a new era of mechanical chronographs.

The successor to Cal.72A, Valjoux Cal.72B

Since 1996, the functioning of the Valjoux Caliber 72B has been completely different from the 72A movement. This movement differs from its predecessor in that it features a Microstella variable inertia balance wheel, which, thanks to screws on the outer circumference of the balance wheel, allows inertia adjustment with emphasis on regularity, without the regulator that was equipped in the 72A movement.
The previous flat balance spring was replaced by a Breguet balance spring, which remained isochronous throughout its expansion and contraction (the "breathing" of the balance spring).
The two screws shown in the picture are part of the variable inertia system.
The microstella screws are on the left side (furthest from the balance wheel in each pair), the thickest control screw is on the opposite right side, and the others are fixed accordingly.



Caliber 72b is also known as 722. The 13-line design (diameter 30mm) maintains a frequency of 18,000 vibrations per hour. The chronograph relies on a column wheel with a coupling yoke.
The Kiff shock absorber with a clover-shaped spring protects the control screw balance wheel and other parts from impacts.
The type of decoration is also different: the caliber featured here has mirror-finished screws and circular-grained bridges. Another feature of this model is the screw-type lever, which was later replaced by a push-type lever.

Caliber: Valjoux 722

I don't think there is a big difference in functionality between the 72B and the Valjoux 722.
However, over time and as a result of maintenance work, it was discovered that there were some parts that were slightly different from what they had originally been.
Looking at the chronograph parts, the standard features include a driving wheel (left side of the photo) and a setting wheel (center of the photo).

The driving wheel, which is essential for the seconds hand, is constantly moving and rotates around the coupling yoke in conjunction with the setting wheel.
When the chronograph is started by pressing the start button, the yoke moves the setting wheel, which then moves with the chronograph center wheel (right side of the photo), transmitting power to the driving wheel (left side of the photo), which then transmits power to the center wheel, and the chronograph hands start to operate.
After pressing the button, the sudden engagement of the setting wheel with the chronograph centre wheel may cause the seconds hand to move forward or backward ever so slightly.
Also note that it says "Swiss Made Fabr. Suisse."

What we would call "stylish" is the placement of the "Rolex Genève" inscription on the dial plate, which distinguishes the 722 from its updated counterpart, the 722-1 (check the enlarged photo below for more details).
As mentioned above, there is no significant functional difference between the 722 and 72B, and Rolex makes no distinction between the two, even in the industrial and technical documentation for the caliber.
Although nowhere to be found in the documents that remain today, small improvements in the quality of the calibers were repeatedly made by the Swiss watch industry.
In fact, instead of the shock-absorbing springs that protected everything, they came up with something more modern, although exactly the same size and function. These technological improvements sometimes led to new products for Rolex.

Caliber: Valjoux 722-1

In 1967, the Daytona was created, powered by the 722-1, which was based on a Valjoux product.
Many watches from that period were equipped with a guard spring to protect the balance spring. This spring contains a metal strip (see photo) and prevents the balance spring from sliding out due to shocks. This modification was also introduced in the 722, but it is not always used in its entirety. Despite its usefulness, due to economic problems, no specific safeguarding spring is installed in today's watches.
The quality of the 722-1 was demonstrated by Rolex using a Valjoux 72A, identical in size (diameter 30mm, thickness 6.95mm) and frequency (18,000 vph).





When Caliber 722-1 was created, one of the improvements that was made was to the parts that operate the 12-hour counter.
In this configuration (pictured above), the chronograph hour wheel (located at 6 o'clock on the dial) is connected to the barrel and is directly involved in the operation of the chronograph.
The new Conveyor is an integral part of the chronograph hour wheel (pictured left), known for its wing-shaped spring and rotating on an eccentric screw, and replaces the simpler function of Calibre 722.
The perfectly adjusted position of the eccentric screw (bottom right of the photo) that rotates the conveyor also ensures better engagement with the 12-hour wheel.
Also note the difference in the placement of the "Rolex Genève" engraved on the plate.