The Compressor Case: History, Design, and Legacy

by Brent Robillard

Introduction

Among vintage dive watches, there’s a certain silhouette that tends to catch the eye—and more often than not, it features two crowns, no crown guards, and a minimalist dial with an internal rotating bezel. It’s a look that screams mid-century function-forward cool, and chances are, it’s based on what collectors affectionately refer to as the “compressor case.”

But the term compressor is one of those pieces of watch-world jargon that gets thrown around a lot—often incorrectly. Many watches today borrow the aesthetic, but few replicate the mechanical principle that made the original compressor watches unique. And that principle? A case that becomes more water-resistant as you dive deeper.

Longines Legend Diver uses a compressor-style case — Contemporary reissue of the Longines Legend Diver @calibre321

The compressor case was developed in the late 1950s by Swiss case manufacturer Ervin Piquerez S.A., better known as EPSA. Their patented system used water pressure itself to increase the case’s sealing capabilities, flipping the usual dive watch engineering logic on its head. The result was a surprisingly elegant solution to the problem of depth-proofing—and one that found its way into dozens of beloved models from brands like Longines, Enicar, Jaeger-LeCoultre, and Bulova.

In this article, we’ll take a closer look at the history of the compressor case, how it works, why it faded from use, and how it continues to influence dive watch design today. Whether you’re a seasoned collector or just figuring out what a Super Compressor is (hint: it’s not a performance-enhancing drug for watches), we’ve got you covered.

Side view of a compressor case and the two crowns — Characteristic dual crowns @calibre321

What Is a Compressor Case?

To understand what makes a compressor case so special, it helps to start with how most dive watches achieve water resistance. Typically, this involves screw-down crowns, gaskets, and case backs that seal tightly to prevent water from entering. The deeper you go, the more pressure the case must withstand — and in a conventional setup, that pressure is just something the seals are designed to endure.

But with a compressor case — specifically one using the original EPSA patent — water pressure isn’t the enemy. It’s an ally.

The case is engineered so that increasing external pressure actually compresses the caseback against its gasket, enhancing the seal the deeper the watch goes. In other words, the deeper you dive, the more watertight the watch becomes. This clever bit of pressure physics gave the compressor its name and earned it widespread adoption in the 1960s and ’70s among brands aiming to produce functional, professional-grade dive watches.

Most compressor watches are immediately recognizable by their dual crowns at 2 and 4 o’clock. One crown operates the time-setting mechanism, while the other rotates an internal bezel — a safer, more protected alternative to the external bezels found on most divers.

Compressor style case with internal rotating bezel and dual crowns — Internal rotating bezel and dual crowns @cal i bre321

EPSA: The Birthplace of the Compressor Case

The true story of the compressor case begins with a Swiss case manufacturer whose name you won’t often see on a dial: Ervin Piquerez S.A., or EPSA for short. Based in Bassecourt, Switzerland, EPSA was one of the foremost case suppliers of the mid-20th century, producing waterproof housings for a wide range of brands — many of which are now highly collectible.

In 1956, EPSA filed a patent for a case design that used environmental pressure to enhance water resistance. This was the original compressor case, and it worked by allowing the case back to flex slightly under pressure, pressing tighter against the case’s rubber gasket as depth increased. This meant a diver’s watch would become more sealed, not less, the deeper it went.

Diagram of a compressor case by EPSA — (Chronopedia)

But EPSA didn’t stop there. They went on to develop what they called the Super Compressor — a refinement of the original idea, typically featuring two crowns and an internal rotating bezel. The Super Compressor branding was never an industry standard; it was EPSA’s own term. Today, it tends to refer to watches that used the later, dual-crown EPSA case designs, though collectors often lump both types together under the “compressor” umbrella.

Over the years, EPSA supplied these cases to dozens of brands — both major players and lesser-known manufacturers. If you’ve handled a vintage Longines Legend Diver, a Jaeger-LeCoultre Polaris, or an Enicar Sherpa, chances are good you’ve seen EPSA’s work in action.

One way to verify whether a vintage dive watch uses an authentic EPSA Super Compressor case? Flip it over and look for the diving helmet logo stamped on the inside or outside of the caseback. That little engraving has become a calling card for vintage compressor collectors.

EPSA dive helmet logo

The Super Compressor vs Compressor Confusion

If you spend any time on watch forums or vintage listings, you’ll quickly notice the terms “compressor” and “Super Compressor” are often used interchangeably. And while that’s understandable, it’s not entirely accurate.

In EPSA’s own terminology, a compressor case was the original single-crown design that used pressure-sealing technology. The Super Compressor was a later evolution — typically identified by its dual crowns, internal rotating bezel, and improved water resistance.

Compressor vs Super Compressor Watch Case — (Chronopedia)

But here’s the twist: Super Compressor was just a marketing name used by EPSA. It wasn’t a technical standard, and it certainly wasn’t used consistently by the brands selling these watches. Many vintage models today are labeled “Super Compressor” even if they don’t technically meet the criteria — and plenty of watches with the dual-crown look don’t feature any actual compressor technology at all.

To make things more confusing, modern brands sometimes produce compressor-style watches that visually mimic the originals but lack the pressure-sealing mechanics entirely. They use the term for aesthetic purposes — not functional ones.

Iconic Compressor and Super Compressor Watches

While EPSA may have produced the cases, it was the brands that made them iconic. Dozens of watchmakers adopted the compressor or Super Compressor architecture in the 1960s and early ’70s, and several of those references have since become collector favourites — not just for their innovative cases, but for their timeless mid-century design language.

Below are a few of the most well-known and collectible compressor-equipped watches.

Longines Legend Diver

Arguably the most recognizable modern revival of a Super Compressor design, the Longines Legend Diver draws direct inspiration from a 1960s reference that featured an EPSA case, dual crowns, and a minimalist internal bezel layout.

The reissue — still in production today — captures the charm of the original, albeit with modern specs and finishing. It remains one of the few widely available watches that wears its Super Compressor heritage proudly, even if the pressure-sealing mechanism has been updated or simplified.

Contemporary reissue of the original Longines Legend Diver on a NATO strap — Longines Legend Diver 39mm @calibre321

Jaeger-LeCoultre Polaris (1968)

The Jaeger-LeCoultre Memovox Polaris from 1968 is not just a Super Compressor — it’s one of the most complex and fascinating uses of the case. This triple-crown diver featured a mechanical alarm function (Memovox), an internal rotating bezel, and a unique triple-case back construction designed to improve underwater acoustics.

JLC’s execution of the Super Compressor format was among the most refined of its era. The modern Polaris collection pays homage to this piece, though — like most current dual-crown divers — the originals still reign supreme in terms of collectibility.

Jaeger-LeCoultre Polaris Memovox diver with triple crown and internal bezel — Jaeger-LeCoultre Polaris (Blommanwatchreport)

Enicar Sherpa Series

If compressor cases had a rockstar era, Enicar was right there on stage. The Sherpa Dive series — especially the Sherpa Super-Divette and Sherpa OPS — featured bold dials, thick markers, and unmistakable compressor cases, making them a favourite among vintage collectors.

Enicar was one of EPSA’s most prolific clients, and it showed in the variety and creativity of their compressor-equipped models. The Sherpa’s blend of dive utility and space-age design makes it one of the most visually distinctive Super Compressors of the era.

A contemporary iteration of the Sherpa OPS with a true compressor case — Sherpa OPS: a true contemporary compressor watch @bowlofsalmon

Other Notables: Bulova, Hamilton, Benrus, Universal Genève

EPSA cases were also used by a wide range of brands that didn’t always become household names in the dive space — but whose Super Compressor models have since developed cult followings. These include:

Bulova Super Compressor “Jumbo”
Hamilton Aquadate
Benrus Ultra-Deep
Universal Genève Polerouter Sub

These watches might not get the same headline attention as the Longines or JLC models, but they offer some of the best value in vintage compressor collecting — assuming you can verify the case back.

Why Compressor Cases Fell Out of Use

Despite their clever design and widespread use in the 1960s and early ’70s, compressor and Super Compressor cases gradually disappeared from the watch landscape. The reasons were practical, technological — and, in some ways, economic.

As the demand for dive watches increased and manufacturing processes improved, brands began favoring screw-down crowns, monobloc cases, and other more standardized methods for achieving high water resistance. These designs were easier to produce at scale, simpler to service, and more versatile in terms of styling.

At the same time, EPSA — the sole producer of true compressor cases — closed its doors in the early 1980s. Without its original manufacturer, the technology didn’t evolve further, and brands that had once relied on EPSA moved on to other case suppliers and construction methods.

It’s also worth noting that the compressor case’s reliance on pressure to form its seal required a level of case flexibility that’s difficult to maintain long-term. With modern materials and gaskets, engineers found more durable and consistent ways to achieve the same — or better — water resistance ratings.

In short, the compressor case was an elegant solution for its time, but improvements in case machining and gasket technology rendered it unnecessary. What remained, however, was the distinctive dual-crown aesthetic and the mystique of a case that actively used water pressure to its advantage.

Modern Compressor-Style Watches

While true compressor cases may have faded from production, their visual influence has never gone away. In fact, today’s watch industry is filled with models that adopt the dual-crown, internal bezel design of the compressor case — even though they lack the original EPSA pressure-sealing mechanics.

These “compressor-style” watches blend the aesthetic charm of vintage divers with the modern engineering standards of today. For many collectors, these new models represent a way to enjoy the compressor look without hunting down vintage pieces — and without the potentially fragile internal pressure-sealing system.

The Baltic Aquascaphe Dual Crown has an internal rotating bezel and two crowns, similar to the EPSA Compressor — Baltic Aquascaphe Dual Crown @mainspring.watch

Brands like Alpina, Baltic, and Christopher Ward have all dipped into the compressor-style trend, offering dive watches that pay homage to the mid-century icons but with updated features and modern water resistance capabilities.

For example, the Baltic Aquascaphe Dual Crown collection includes models with dual crowns and internal bezels, mimicking the visual style of the original compressor cases. However, these modern watches are built with high-tech gaskets and robust screw-down crowns for a more reliable seal — a perfect blend of vintage aesthetics and contemporary practicality.

Traska Seafarer is a modern interpretation of the compressor style watch case — Traska Seafarer @calibre321

Another popular model is the Traska Seafarer, which, although not technically a compressor case, adopts the internal rotating bezel design reminiscent of the vintage Super Compressors. With a high-strength stainless steel case and 3-D printed lume blocks, it’s the perfect example of how modern technology can combine with retro design.

Ultimately, while these modern watches may not feature the original compressor technology, they still carry the spirit of innovation that made the original designs so legendary. Whether you’re looking for a nostalgic piece that looks like a Super Compressor or simply want a robust, reliable dive watch, the compressor style has you covered.

Why Compressor Watches Still Matter

Despite being largely relegated to the vintage market, compressor and Super Compressor watches still hold a significant place in the world of horology. Their legacy continues to influence contemporary dive watch design, and they remain a key part of the mid-century dive watch aesthetic that so many collectors cherish today.

At the heart of this is their unique engineering solution — the idea of using water pressure to increase the effectiveness of the case’s seal. This clever, albeit short-lived, approach set the stage for the more complex water resistance systems we now take for granted. It’s a reminder that even the most niche innovations can have a long-lasting impact on the way we understand and appreciate dive watches.

Moreover, the compressor case aesthetic — especially the dual crown design and internal rotating bezel — has become emblematic of vintage dive watch charm. Even today, modern watches that carry these design elements tap into a sense of nostalgia and history, making them appealing to a new generation of collectors who may not have the budget or inclination to pursue the originals.

In short, compressor cases may no longer be the cutting-edge solution for dive watch design, but they represent a crucial chapter in the development of professional timepieces. For collectors, owning a vintage Super Compressor or a modern homage piece is a way to hold a piece of horological history in their hands — and dive into the legacy of innovative Swiss watchmaking.

Whether you’re chasing after an Enicar Sherpa, a Longines Legend Diver, or a more modern example from Baltic or Christopher Ward, the influence of the compressor case is undeniable. It’s a testament to the fact that even in the world of modern, hyper-accurate dive watches, the classics will always matter.