4130 - diameter: 30,50 mm, thickness: 6,50 mm
3235 - diameter: 28,50 mm, thickness: not found
Copy from an
article by Ashton Tracy
"Another factor to consider is that the 3235 has a movement diameter of 28.5 mm. Let’s compare this with a 4130, the in-house Rolex chronograph movement, which also has a power reserve of 70 hours.
There is no Chronergy escapement here; Caliber 4130 contains a standard lever escapement. Admittedly, it is 2 mm larger in diameter, coming in at 30.5 mm; however, it incorporates a three-register chronograph.
How did Rolex achieve this this feat? By installing a longer mainspring into a barrel with regular-sized walls. This barrel doesn’t need replacing every service – a new mainspring will do just fine.
So why couldn’t this have been an option for the 3235? Perhaps to make the servicing and the acquisition of parts more difficult? Perhaps there was truly no more space to install a larger barrel? I’ll let you be the judge of that one.
Increased power reserves are definitely a win for the customer: people don’t enjoy having to set their watches frequently, which can become tedious.
Additionally, the less the wearer has to adjust his or her Oyster watch, the less likely water-resistance problems will arise. I have no issue with a modern caliber outlasting an older counterpart by many more hours, but I do take issue with the way it has been achieved in this particular case."