Exceptional Movements In History: Rolex Caliber 1575, The Watchmaker’s Watch
by Ashton Tracy
Rolex is known for producing quality, dependable movements that get the job done. We need only survey the brand’s current lineup of calibers to see that for the last several decades, quality and functionality have been at the forefront of Rolex engineering.
The 3135 introduced in 1988 has been the workhorse behind so many models as the base caliber for complications including second time zone and day/date.
In recent years, however, the 3135 has taken a backseat in lieu of the 32xx family, which has started to shine. It is my educated assumption that the 31xx movement family will be completely phased out in coming years, to be entirely replaced by the 32 series.
But a long time ago, before these movements reigned supreme, the Rolex world relied on the 15xx series to keep it on time.
Rolex Caliber 1575
As far as automatic watch movements are concerned, the Rolex 1575 is the cream of the crop: it has it all. It’s hard wearing, robust, elegant (ish), and an exceptional timekeeper.
Interestingly, when these movements leave a Rolex service center after an overhaul, they are sent out to run within C.O.S.C. specifications, meaning to gain two seconds per day. That’s quite a feat for a watch of that age; different brands’ watches of similar pedigree don’t produce those results many years later that I’ve seen.
Rolex Caliber 1575: brief history
The 1575 was launched in the mid-1960s. As it movement it doesn’t have a particularly grandiose history; Rolex produced it because it needed a reliable, robust automatic watch. And, boy, did it deliver. Job done.
Caliber 1575 was based upon the Rolex 1560 movement, but improvements were naturally built in. The 1560 had a frequency of 2.5 Hz and a power reserve of 44 hours. When the 1575 was launched it was based heavily on the 1560 but with a few upgrades; most notably a four-hour power reserve increase, a frequency increase to 2.75 Hz, and hacking seconds.
Rolex Caliber 1575: movement specifics
The 28.2 mm diameter movement features 25 jewels, date display, and overcoil balance spring.
The finishing is nothing to write home about as functionality was definitely at the forefront of the designers’ minds. The main plate features a spotted pattern, and the bridges boast a lightly grained finish.
Functionality and ease of repair are where the 15 series family shines. The barrel bridge is solid, yet not cumbersome, housing only the barrel underneath. The train wheel bridge secures all the train wheels under one roof, as it were.
Of particular note is the shock protection feature for the escape wheel. It is an unusual feature that is most commonly saved for balance wheel pivots. I have seen it on other calibers, but rarely and only on the movement side, which indicates it’s for show more than functionality. With this Rolex caliber, however, we see the escape wheel on both dial and movement side.
Its escape wheel pivots are fine in nature, and I find that having this extra protection is a definite positive. This is a feature Rolex uses down to this day in most, if not all, of its movements.
The balance features timing screws plus two microstellar nuts to adjust timekeeping. These nuts are turned either clockwise or counterclockwise to adjust the rate of the watch, depending on what is needed.
The 1575 uses a free-sprung balance, which means regulating pins are not required. Regulating pins are used to control the active length of the hairspring, thus determining timekeeping. Their downfall is that if the watch receives a shock the pins can move, resulting in a timing error. With a free-sprung balance that can’t happen as there are no pins; timing is controlled via the balance itself.
The oscillating weight is heavy and has the mass to get the job done. It features a center axle rather than ball bearings, and is held in position by two ruby jewels, thus reducing friction and improving performance. This again is a feature that Rolex used throughout the 30 and 31 caliber families.
Much like the oscillating weight and shock protection for the escape wheel, the instantaneous date function of the 15 family is something Rolex uses to this day.
Firstly, though, let’s get this out of the way: there is much confusion about the date model for the 15 series, but do note that the 1575 is not a GMT movement; it is a date-only model.
The movement called “1575 GMT” is the one that features a GMT complication.
And to further complicate things: when the watchmaker opens a watch powered by a 1575 movement, the bridge may well be stamped “1570.” This is not incorrect; it is merely something that happened back in the day.
The date changes at midnight and it does so instantaneously using a cam, spring, and jewel. The cam has a cutout for the jewel to sit neatly within, and as the watch gets near midnight the lever with the jewel attached is forced into the cutout of the cam, enabling the date to change at exactly midnight.
Rolex Caliber 1575: conclusion
The 1575 is most definitely the watchmaker’s watch. It is a pleasure to work on, can be made to perform exceptionally decades after production, and never becomes tedious.
It is also the consumer’s watch as it keeps great time, remains as robust and reliable as when it left the factory floor, and it simply gets the job done. It might not be the most elegant or visually appealing movement in history, but when something needs doing right, it gets the job done.
Quick Facts Rolex Caliber 1575
Production years: 1965-1981
Frequency: 2.75 Hz/19,800 vph
Height: 6.3 mm
Power reserve: 48 hours
Functions: hours, minutes, center seconds, date