Hands-On: The Citizen Eco-Drive One, An Ultra Thin Light-Powered Quartz Watch With A One MM Thick Movement

We've been looking lately at ultra thin mechanical watchmaking; let's take a look, now, at one of the thinnest wristwatches in the world of any kind. The big release from Citizen this year is a very unusual one: an Eco-Drive (solar-powered quartz) wristwatch with a 1-mm-thick movement, in a case less than 3 mm thick. Making a watch this thin that works reliably and is reasonably durable takes not only cutting edge movement design, but also very careful case design.

The current record holder for world's thinnest mechanical watch is, of course, the Piaget 900P, at 3.65 mm. The construction of the 900P is what's behind its drastically reduced thickness. The limiting factor in mechanical horology, in terms of thinness, is probably the height of the mainspring barrel; beyond a certain point, if you get too thin there just isn't enough power to get adequate energy to the balance. In quartz watches, you can suppress thickness even more dramatically. Integrated circuits can be mere microns thick (thin-film circuits, two microns or less) and the limiting factors in a light-powered quartz watch are probably the capacitor, the stepper motor driving the hands, and the added thickness of the solar cell. Still, 1 mm thick for the movement and 2.98 mm for the watch overall is nothing to sneeze at.

This is not the thinnest quartz watch ever made, of course. That record is held by the Concord Delirium, which was first released in response to the release of ultra thin quartz watches made by Citizen and Seiko in 1978 (4.1 mm and 2.5 mm thick, respectively). The Delirium was released in 1979 and was only 1.98 mm thick. The thinnest version of the Delirium was basically unwearable, at .98 mm – so thin that if you tried to strap it on, the case would flex so much the watch would stop. However, I'm not aware of any thinner solar-powered watch on the market now, or for that matter, ever made.  

The model shown is the first of four versions that Citizen has announced. This is a limited edition model with a Cermet (ceramic and metal composite) case; the bezel is "binderless cemented carbide," which, it seems reasonable to assume, is sintered tungsten carbide (Citizen says "tungsten carbide powder with no metallic binder.") This should make for an extremely rigid and, for all intents and purposes, scratch-proof case. That model is the most expensive of the four, thanks to the exotic materials for the case and bezel, as well as the nature of the movement: $6,000. Three other models, with stainless-steel cases and Cermet bezels, have also been announced; these models will all have stainless-steel bracelets and cost $2,600.

Case diameter is 38.15 mm; it wears bigger thanks to the narrow bezel. In its own way this is a pretty head-turning watch; obviously at $6,000 the limited edition (800 pieces globally) is for a niche audience, but at $2,600 the other three models are in their own way spectacular examples of the ongoing development of quartz watch technology. They're extremely thin, obviously, but also reasonably practical, unlike many ultra thin watches (and, probably, able to run for many years without human intervention).

The Citizen Eco Drive One: As shown, limited edition of 800 pieces worldwide, price, $6,000. Case, 31.85 mm x 2.98 mm, "water resistant" per Citizen, but not otherwise specified. Reference AR5014-04E. Case, Cermet; bezel, sintered tungsten carbide. Movement, Citizen in-house caliber 8826, light-powered Eco-Drive, maximum variation in rate +/- 15 seconds/month; 10 month power reserve (if left in complete darkness). Visit Citizen online here.

For your mobile reading pleasure, with years of archived watch content plus new stories, breaking news, and access to great new features like HODINKEE Live, download the HODINKEE mobile app, free on iOS.