Diving with the New ZRC Grands Fonds Heterium

ZRC is a Swiss brand that seems to live on the shadowy periphery of the watch world. Despite being founded over 120 years ago, I can count the times they have come up in casual watch conversations on no hands. That is to say, it never happens. Even when I agreed to take this new ZRC Grands Fonds Heterium for a diving test and check it out, I was thinking to myself, “Those are the ones with the crown on the bottom right?” and “…something to do with the French Navy?” This represented my entire knowledge of the brand, so I was excited to do some research and finally learn a concrete fact or two. After digging into it, I have concluded it’s a crying shame that we don’t talk about ZRC Watches more often, so hopefully we can turn over that new leaf together, starting right here and right now. Let’s start with a little history.

Brand History

Founded in 1904 in Geneva by Edmond Zuccolo and Joseph Rochet, ZRC spent their early years as a purveyor of chains for pocket watches. They also created the first-ever claw bracelets, to allow pocket watches to be worn on the wrist. This would put them up there with the pioneers of the early days of wristwatches, but who did that first is a debate for another time.

In 1917, ZRC won the highly-coveted Prix de l’Industrie Nouvelle de Genève (Geneva Prize for New Industry) for developing the first-ever extendable metal watch bracelet, and they would spend the next few decades specializing in watch bracelets and straps, while also manufacturing watch cases for other private-label brands. Beginning in the 1930s they would start to specialise in making waterproof watch cases in order to meet the increased demand from new military applications and technologies.

In 1958 Mr. Yves Pastre, a local watchmaker and shop owner in Toulon, France, gave ZRC’s commercial director at the time, a certain Mr. Bourdain, an idea: the French Navy was looking for a waterproof watch supplier, and since ZRC already had years of experience building waterproof watch cases for others, why not make one of their own and make a bid on the contract? The resulting project and bid was a success. This would be the beginning of the ZRC Grands Fonds line of watches and they would go on to equip French Naval divers for the next 35 years, until 1995.

Jump ahead to 2014 – Georges Brunet, the great-grandson of founder Joseph Rochet, decided to produce a re-release of the Grands Fonds to commemorate the 110th anniversary of the company’s founding. Some production and development issues would delay that a bit and it was actually released in 2015 for the company’s 111th birthday, but close enough! The GF300 was released in a limited edition of 300 pieces and the Grands Fonds had been reborn. With the success of this release and a growing public appetite for the stories and lore of vintage dive watches, Mr. Brunet decided to fully relaunch the brand and the Grands Fonds line in 2018.

The ZRC Grands Fonds Heterium

Now, in 2025, ZRC has two lines of dive watches: the recently launched Securicode line, which is a tribute to their very first dive watch back in the 1960s, and the flagship Grands Fonds line, one of which we took diving and will talk about here today, the ZRC Grands Fonds Heterium.

The modern standard in the Grands Fonds line is called the Réédition, their pure, black dial no-date dive watch. This Heterium is that same watch but with a lovely blue-to-black gradient dial. This is a 41.5mm stainless steel Tool watch with a capital T. Considering the modern brand has NEVER produced a watch that was not a dive watch, we should expect nothing less. The angular, almost brutalist case is all business, as is the very recognizable crown at the 6 o’clock position, a Grands Fonds trademark. This was done to keep the crown out of the way and to employ a unique fail-safe feature using the cutout in the bracelet or strap, the CPS or Crown Protection System. The size of the little cutout makes it impossible to wear the watch unless the crown is in the fully screwed-down position, eliminating the possibility of accidental flooding due to user carelessness. You technically can wear it in the incorrect position but the bracelet doesn’t articulate fully and you can tell something is wrong. It takes a bit to get used to manipulating the crown in this position (also because it screws down in the opposite direction of a standard crown), but it’s second nature once you get the hang of it.

The gradient blue dial is lovely to look at and also highly legible, partly due to the large blocky sword hands and partly due to having Super-LumiNova everywhere, from the applied indices to little internal pips off of every hour marker to the large hands to the inlaid bezel markers. The black ceramic bezel features another bit of patented and acronym’d ZRC technology. The ECS, or Easy Clean System, is a little slot on top of, and a channel running all the way through the bezel that allows fresh water to be circulated through to prevent the buildup of salt between the bezel and case, which can cause corrosion over time. I have personally never spent enough time with one watch in salt water to have this be a problem, but it was implemented after a suggestion from Yves Pastre, watchmaker to the French Navy, so that’s good enough for me. Whether you need this feature in your day-to-day life or not, it’s an interesting bit of tech.

ZRC specialise in something called “programmed deformation of materials” which according to Google refers to “designing materials with specific and controllable deformation behaviours under certain conditions.” This scientific approach allows them to make watches that are water-resistant to great depths without having to resort to super-thick cases and crystals to do so. Indeed, this watch is rated down to 1,000 metres, well beyond the dive watch standard of 300 metres, yet is somehow only about 13mm thick, and 14mm counting the crystal. It’s certainly the thinnest 1,000-metre diver I have ever handled – and keep in mind that it’s actually tested to 1,500m.

The case back is yet another interesting piece of technology, with a mechanism borrowed from the way submarine hatches close and seal. From ZRC, “the caseback is composed of 2 distinct parts. A clamping ring puts pressure on the shielded back which then applies a vertical pressure on the gasket. Therefore the armoured back remains ‘free’ and will accompany the ambient pressure that it relays on the joint in order to balance the pressures without ever compromising the case.” I will need to see that in a video to truly understand the inner workings but it certainly sounds cool, and anything that makes for a thinner deep-dive watch is a victory.

Yet another interesting and unique part of this watch is the bracelet, no surprise since ZRC spent years working as a bracelet manufacturer. It is a strange combination of one extra-long link, then an open, ladder-style link, and then normal links coming off each side of the case. The extra-long links each have a built-in spring system, which works as a diver extension without having to deploy anything, as it automatically stretches to fit over a wetsuit. It’s a brilliant little feature that I now want in every bracelet across the board. The clasp is also unique, being a small hook that you use to fasten each end, and then a small rotating piece of metal covers the connection to keep it in place. It’s a little tricky to put on by oneself, especially over a wetsuit, but otherwise it is by far the most interesting bracelet I have seen since the first Tudor Pelagos bracelet came out.

The movement inside is the Sellita Elaborate SW300-1. The top-tier version of this well-known automatic movement (an alternative to the ETA 2892) beats at 28,800vph with a power reserve of 56 hours and is rated to +/- 5 seconds per day, which is close to COSC spec without actually being COSC certified. That covers all the specs so now let’s take it diving.

The Grands Fonds Heterium In The Water

We took the ZRC Grands Fonds Heterium on a few shipwreck and reef dives down south Florida and it proved to be an excellent diving companion. I tried it on the bracelet and the rubber strap, and while my preference would be the bracelet, the difficulty of putting it on without help from a buddy would probably lead me to opt for the rubber strap if this was my watch frequently used for diving. Either option was very comfortable and the fact that ZRC has used screws to attach the strap instead of the usual spring bars means there is little worry of the watch popping off under the rigours of scuba diving. The 60-click bezel sets easily and has a very satisfying action. My only critique is there could be a little bit more grip or maybe a slightly larger bezel to help with articulation, as it’s very thin, especially with a gloved hand.

Underwater the watch is highly legible due to the slightly reflective nature of the dial and the copious amounts of lume. The larger minute hand never left any doubt as to how long I had been underwater at a quick glance. It would be a little easier to calculate with actual numerals on the bezel but it would take away from the aesthetics so I think that’s a fair trade-off for what is effectively a backup timer anyway. From an aesthetic and romantic standpoint, the watch has tons of vintage charm and gives you the feeling you could be doing something important like smoking cigarettes on deck with Jacques Cousteau or clearing harbours of explosives with the French Frogmen of the 1960s, and don’t we all want to feel like that at least once in a while?

Final Thoughts

The more I learned about ZRC researching this article, the more surprised I became that they seem to get so little recognition, as their technical and military chops put them up there with the Tudors and Rolexes of the watch world. Maybe that’s for the best, as watch enthusiasts love the proverbial “secret handshake.” But, since Mr. Brunet said they are working on more expansion of the brand and also on impending chronograph and GMT models, I think it’s safe to say that this secret club won’t be a secret very much longer.

Now available from authorized dealers for CHF 3,290 on rubber strap and CHF 3,690 on steel bracelet. More info at zrc1904.com.