The Rolex Caliber 3155

While it may have the reputation for never letting the grass grow under its feet in terms of technical development, Rolex could never be accused of tinkering with its designs just for the sake of it. If they develop a significantly improved process or system or material that will genuinely add something to one of their watches, that watch will be updated. Otherwise, it will be left well alone.

It leaves the brand using certain elements for decades, proof that they are as good as it is possible for Rolex to get them—which usually means they are the best they can be.

The Cal. 3155 is one such example. Introduced in 1988, it still powers the 36mm versions of the brand’s flagship Day-Date model today, nearly 30 years later.

Perfectly Simple

Of course it helps with the longevity of their movements that, until very recently, the brand has rarely ventured into ultra complicated territory. Their backbone has always been the kind of elegant, dignified, but above all, simple watches that require calibers to just tell the time, with perhaps an occasional date wheel to tick over. Before the Yacht-Master II’s regatta countdown and the Sky-Dweller’s annual calendar, the Day-Date was as complex as Rolex got, or needed to get.

A derivation of the all-conquering Cal. 3135, recognized as perhaps the most consistently accurate and reliable automatic mechanical caliber ever made, the Cal. 3155 served as the replacement for the Cal. 3055—which was itself an extremely highly regarded movement, and powered the President for some eleven years.

But it was obvious to even the most casual observer what the upgrade was going to bring to the party. While the outgoing 3055 had introduced the convenience of a Quickset function to the Day-Date, it was only possible to set the date of the month with the crown—what is known as a single Quickset. The new mechanism allowed for the day of the week, displayed at the twelve o’clock position, to be adjusted instantaneously as well, without having to spin the hour hand through countless revolutions.

It was a perfect example of the Rolex philosophy; incremental improvements designed to make their products perform better in a very real sense, rather than a superfluous, ‘look-at-me’ add-on.

The Cal. 3155 vs. the Cal 3055

To further underline the level of perfectionism at the heart of Rolex, with the exception of the Double Quickset function, the new movement and its predecessor are virtually identical in every other respect.

Both Perpetual calibers have the smoothly sweeping seconds hand of an engine running at 28,800vph, and each use the well-proven arrangement of a free-sprung Nivarox hairspring and Breguet overcoil, with a Microstella regulated Glucydur balance wheel.

The addition of the extra Quickset complication bumps the jewel count up from 27 to 31, but other than that, the two movements share the same power reserve at 48 hours and even their dimensions are similar; the Cal 3155 loses 0.3mm off its waistline even with the added functionality, weighing in at 28.5mm in diameter and 6mm deep, against the older mechanism’s 6.3mm.

Both calibers pre-date Rolex’s latest major innovation, the Parachrom Bleu hairspring, that brings an unrivalled level of magnetic and temperature resistance to the range. First making it into the series inside the Cal. 3156 designed exclusively for the short-lived Day-Date II, it is also a vital part of the makeup for the Cal. 3255, the power behind the genre busting 40mm Day-Date released in 2015.

Even without the advantage of Parachrom technology, the Cal. 3155 effortlessly won its Chronometer status from the COSC, rating it as accurate to within -4/+6 seconds a day. Seemingly not good enough for the higher-ups, since last year, all the brand’s watches have been subjected to even more ferocious tests designed by Rolex themselves, requiring a precision of -2/+2 seconds a day, both on the movement alone and again once fitted inside the case. Only those mechanisms that live up to the mark can wear the Superlative Chronometer tag.

The Cal. 3155 at Work

The first watch to display both the date and the day of the week when it was launched back in 1956, the Day-Date was an instant hit, stealing the flagship crown from the Datejust, and finding its way onto the wrist of some of history’s most renowned heavyweights.

It gained its ‘President’ nickname from both its synonymous bracelet, specially created for its debut, and its association with a long line of commanders-in-chief. From Roosevelt to Johnson and Nixon to Reagan, all were proud wearers of the Day-Date. JFK was a brief recipient, and anything but proud, receiving his as a gift from Marilyn Monroe following her scandalous rendition of ‘Happy Birthday, Mr. President’ in 1962. The watch was quickly disappeared—the actress followed three months later.

In more recent times, leaders across vastly different fields have worn the President. From board chairmen and women, to hip-hop artists and sports legends, the sheer diversity of styles appeals to just about every taste.

Only available in precious metals, the Day-Date can be made to shout for attention or remain the strong and silent type. In yellow gold with a diamond bezel, it’s the life and soul of the party; in platinum with a black dial, it’s reserved and introspective.

And underneath it all, ticking away with the sort of reliability only achieved by the cumulative effects of a relentless pursuit of perfection, a Rolex caliber goes about its understated business.

The Cal. 3155 epitomizes the brand. It does everything it needs to do and nothing more. But what it does, it does better than anything else.