Repost from Gear Patrol.  Original article by Allen Farmelo / Photos by Rolex

Deciphering the nuances that distinguish, say, a 1970 Rolex Submariner from a 1980 version can require the sharp eye of a forensic analyst and the patience of a research librarian. Indeed, Rolex experts tend toward detailed taxonomies of minuscule modifications, and Rolex does indeed introduce these incremental annual updates to the point where many modifications seem more mythical than material. People new to Rolex face mountains of such information, and that can make getting to know the brand intimidating and confusing.

If we drop the year-to-year analysis, however, and stick to the current offerings, the Rolex catalog is actually quite easy to understand. Rolex makes relatively uncomplicated movements, formulates five case alloys, offers five types of bracelet, two types of clasp, a handful of bezels, some dial variations, and with just these components the Crown builds out its entire catalog. Get a loose grip on the basic building blocks, and the entire Rolex oeuvre becomes surprisingly simple to navigate.

Model or reference numbers within a particular series of watch (Submariners, say) tend to follow an evolutionary scheme (to wit: the modern Rolex GMT Master II with Pepsi bezel is the 126710BLRO, which sounds like a mouthful — but when you realize that the ref. 16710 was the last generation of the “Pepsi” bezel-quipped GMT Master II that Rolex produced before the current one came out, you can see how one reference number evolved into the next one).

Oyster: This is the name that Rolex’s founder, Hans Wilsdorf, gave to the earliest waterproof watches from the 1920s. “Oyster” remains the essential metaphor for Rolex, and it shows up in a number of phrases, model names, and neologisms.

Cyclops: Patented by Rolex in the early 1950s, this is a magnifying device that makes the date appear larger. Originally part of the crystal on early plexiglass models, the Cyclops later became an added piece of glass on sapphire crystal-equipped models that was glued to the main crystal.

Helium Escape Valve (HEV): Originally co-developed by Rolex and Doxa, this is a small, spring-loaded one-way valve that is integrated into a watch case and allows helium and others gasses to escape the watch as a SCUBA diver ascends following a dive to great depths. Originally developed for commercial saturation divers who found that the crystals on their watches were popping off in decompression chambers as the pressure within the watch equalized to that of the outer environment.

Rolex formulates and produces most of its materials in-house. Discounting a number of esoteric materials used specifically in Rolex movements, nearly all Rolex watches are made from just nine materials.

Oystersteel: As part of the 904L family of steel, Oystersteel can achieve the corrosion resistance and high polish of precious metals.

Everose Gold 18k: By adding copper and silver to its formula, Rolex achieves its uniquely warm rose gold.

Yellow Gold 18k: This alloy is proprietary, trusted, and has an iconic hue.

White Gold 18k: Rolex’s white gold seems to radiate light.

Platinum: Rolex uses 950 platinum exclusively (and sparingly). 950 is a high-concentration alloy that includes ruthenium for strength and shine.

Rolesor: Not really its own metal, this is a name Rolex gives to its patented method of combining Oystersteel and gold in its many two-tone models.

Cerachrom: Rolex’s proprietary ceramic is scratch-proof, impervious to UV rays, and is the current standard for the bezel inserts on Rolex’s sport watches.

Precious Stones: Name it, and Rolex has likely mounted it to a watch, but diamonds are most common.

Chromalight: Rolex’s lume. Blue by night, bright white by day.

Crownclasp/Crownlock: The dressy and sophisticated bracelet-locking mechanism that virtually disappears once secured.

Oysterclasp/Oysterlock: This is what Rolex calls its most popular and most secure deployant clasp. In includes a secondary locking mechanism that folds over the main clasp.

Easylink: This simple mechanism allow you to expand a bracelet by 5mm, handy when swelling occurs on an airplane or, perhaps, after a big meal.

Glidelock: Rolex’s patented bracelet extension mechanism that allows for up to 20mm of adjustment in 2mm increments for use over wet suits.

Jubilee Bracelet: The refined five-piece links make for a dressy look, but the Jubilee remains a staple of Rolex sport watches, too. Offered in the various metals plus the three Rolesor combinations, the Jubilee can be fitted with either an Oysterlock or a Crownlock clasp.

Oyster Bracelet: The larger three-piece links make for a simpler, sportier look. Oyster bracelets only ship with Oysterlock clasps.

President Bracelet: Less common, the President uses elegantly rounded three-piece links and only comes with a Crownlock clasp.

Pearlmaster Bracelet: The refined five-piece links make the Pearlmaster Rolex’s most elegant bracelet. Crownlock clasp only.

The Rolex Leather Bracelet: Offered in a variety of colors and hides, Rolex’s in-house leather straps are fitted with Oysterlock clasps or a simple pin buckle.

Oysterflex Rubber Bracelet: Few rubber straps will blow your mind, but the Oysterflex just might. The attention to detail and innovative design add up to suppleness, comfort, and style. Oysterflex bracelets are fitted with Oysterlock clasps.

Plain Bezels: As basic as you’ll find on a Rolex, plain bezels can be had on a number of models in steel and in precious metals.

Fluted Precious Metal Bezels: Iconic and hard to miss, today’s fluted bezels are offered in precious metals only.

Engraved Fixed Bezels: Found only on the Explorer II and the Daytona Cosmograph, demarcations are engraved into either Oystersteel, a precious metal, or Ceracrom.

Rotating Bezels with Inserts: The classic for the Professional watches, scratch-proof Ceracrom inserts are the norm.

Rotating Precious Metal Bezels: Exclusive to the Yachtmasters, these deeply engraved bezels achieve a compelling balance of sportiness and elegance.

Bejeweled Bezels: Rolex has encrusted just about every bezel with precious stones at some point.

You can pretty much get by knowing only about Rolex’s 3000-series auto-winding mechanical movements and a few smaller 2000-series versions. Beyond that, we’re really only talking about the Sky-Dweller’s Ref. 9001 and the Daytona’s Ref. 4130.

3255: Introduced in 2015, the core technologies of the 3255 will likely soon be the basis for a majority of Rolex’s movements. Rolex claims that the 3255 handily doubles the accuracy of +6/-4 secs/day set out by Switzerland’s official accuracy testing program, COSC.

3135: Only incrementally changed since 1988, the 3135 still forms the basis of most modern Rolex movements. It includes an instantaneous date change at midnight, a classic Rolex feature. The 3135 is the basis for many variations.
3155 — day-date complication
3130 — no date
3131 — no date, with anti-magnetic shield
3132 — no date, with Paraflex anti-shock system
2235 — smaller with date (2236 gets an updated hairspring)
2230 — smaller without date

3186: Rolex’s 24-hour GMT movement (the 3187 picks up the Paraflex anti-shock system).

9001: Rolex’s most complicated movement with two time zones and an annual calendar (Sky-Dweller only)

4130: No-date chronograph movement (Daytona only)

Oyster Perpetual Professional (7 models): Rolex’s most robust, purpose-driven sport watches.

Oyster Perpetual Classic (6 models): Dressy yet sporty, always waterproof, always classic.

Cellini (4 models): Traditional, sometimes complicated, moderately waterproof.

Read the complete article and buying guide at gearpatrol.com