DELMA SHELL STAR DECOMPRESSION TIMER

By 1975, Delma had established itself as a brand that could build rugged divers’ watches worthy of professionals. These were called the Shell Star and Quattro, cased in stainless steel with the requisite rotating bezel.

Reaching back into its history, Delma rebooted the Shell Star collection in 2016 with a model that retained the spirit of the original but included up-to-date technology. It was outfitted with a helium valve and water-resistant to 500m.

The Delma Shell Star Decompression Timer is the latest addition to the Shell Star family, and she arrives decked out in some mighty fine functionality. Hope the other kids won’t be jealous. As you can see, the dial is chock full of indications. Don’t be overwhelmed, the layout is actually very clear and easy to read. So, what are we looking at? Get ready to geek out.

You probably know that when you go deep diving, you can’t safely rise to the surface all at once. The rapid change in pressure upon ascent causes Decompression Sickness, also known as the bends. To prevent this from happening, divers must come up gradually, staying at certain levels for periods of time before rising further. But how do you know where to stop and for how long?

During the 1950s and 60s, Swiss divers Hannes Keller and Albert Bühlmann, buddies from the University of Zurich, recognised the relationship between altitude and decompression. With their combined expertise in maths, physics and diving, they developed tables showing specific gas mixtures for different elevations, along with decompression stops. Not only were their tables applicable underwater, they also proved useful on land. The Swiss military adopted them in 1972 for use in the mountains.

Once you know what you’re looking at, the information on the dial pops into relief: Keller and Bühlmann’s table at the ready. As you can see the scale shows depth in both metres and feet, along with white rectangles signifying the no-decompression limit (NDL), and another scale showing decompression stops with the duration indicated by numbers.

Baton-style hour indications receive luminescent treatment as well as the hour and minute hands along with the central sweep seconds. This latter indication is a requirement for a diving instrument. And yes, the date makes it to the party at 3 o’clock.

Grab a hold of that unidirectional bezel and you get a satisfying click. While a lot of companies have chosen to go with an updated ceramic bezel, the Shell Star Decompression Timer keeps it classic with an aluminium insert. Aluminium does fade over time, but that gives the watch character and shows it’s been loved.

The 44mm tonneau-shaped case in stainless is really shapely. It incorporates a helium valve and is water-resistant to an impressive 500m. The case frames the dial, guiding your attention to where it needs to be, rather than distracting the wearer’s attention away from the essential indications. A bit of a puzzler is why Delma chose an exhibition caseback for an unfinished, stock Sellita movement. Granted it’s a workhorse that reliably gets the job done, but if you’re going to make a point of opening up the hood, it would be good to see a little decoration on the engine.

The Delma Shell Star Decompression Timer is offered with a stainless steel bracelet and deployant clasp or on a genuine rubber strap with stainless steel buckle. The dials are offered in blue or black with the latter shade being offered with a choice of a black or orange bezel. Everything comes neatly packaged in a Delma blue box.

While only a rarefied few will ever test the specs or need the advanced tables for decompression diving, it’s still cool to have a bulletproof watch at the ready, especially one offered at a very reasonable price. Moreover, you’ve got a cool story to tell when people ask you what the chart on the dial is for.