Zenith Updates the Chronomaster Open with their Next Gen El Primero 3600 Caliber

Zenith’s open heart chronographs are watches that aren’t often talked about in enthusiast circles, but they are nonetheless a core component of the brand’s lineup, and have been for years. Watch hobbyists, I think, tend to be less interested in the novelty of seeing part of the movement through the dial side for a number of reasons. Unless it’s showing you something legitimately special (like a tourbillon), most collectors would rather have an unobstructed view of a great dial than have that dial broken up to see movement components that might be industrially finished, or not particularly dramatic from the front. But there’s no denying that for consumers who are new to mechanical watches, there’s a novelty and romance to seeing the movement in action whenever you glance at the time, and Zenith reminds us that there’s a difference in how these open heart displays are executed from brands at the entry level to those who sit higher up on the luxury spectrum.


Zenith introduced the Chronomaster Open in 2003 as a means of putting their high frequency El Primero caliber on display, and according to Zenith it was the first time in watchmaking history that a chronograph had been produced with a partially open dial to reveal the escapement. Nearly 20 years later, Zenith has updated the Chronomaster Open to highlight their latest El Primero 3600 caliber, which features timing to the tenth of a second thanks to a chronograph seconds hand that’s coupled directly to the escapement. The importance of the escapement design in the new 3600 caliber provides a natural link to earlier Chronomaster Open models from a historical perspective. While a brand producing an open heart dial with off-the-shelf movements might feel somewhat gimmicky, it makes sense for Zenith given their history and the nature of the movement itself. It’s a well earned flex. 

As a refresher, the El Primero 3600 behaves differently than a typical chronograph caliber. The central chronograph hand, rather than counting the seconds with a full rotation around the dial every minute, provides a tenth of a second reading, whipping around the dial once every 10 seconds. In person, this is actually somewhat jarring at first, and is undeniably impressive and visually interesting. How practical it is really depends on your timing needs and your own reaction time. Mostly, this is Zenith moving the engineering ball forward in impressive fashion. Considering that this movement was only introduced a year ago and is now found throughout the Zenith chronograph lineup is actually quite an achievement. 

The dials here are a new spin on the tri-color configuration that the El Primero is known for. In previous Open models, the small seconds counter at 9:00 would have been entirely removed (to see the movement, naturally) , but on these new watches use a small piece of hesalite crystal at that 9:00 opening to create a sub register that is still readable while allowing a view of the escapement below. Credit to Zenith here for rethinking the main draw of these watches in a subtle way rather than simply recreating a 20 year old dial design with a new caliber behind it. 

The cases here are 39.5mm in diameter and trade on vintage cues from historical El Primeros. Dials are available in white or black variants, and can be purchased on either a matching stainless steel bracelet or Zenith’s cordura rubber strap. The retail price is $10,000. Zenith

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Zach is a native of New Hampshire, and he has been interested in watches since the age of 13, when he walked into Macy’s and bought a gaudy, quartz, two-tone Citizen chronograph with his hard earned Bar Mitzvah money. It was lost in a move years ago, but he continues to hunt for a similar piece on eBay. Zach loves a wide variety of watches, but leans toward classic designs and proportions that have stood the test of time. He is currently obsessed with Grand Seiko.