In Jim Manley’s write-up of the Melbourne Collins, he asked, “Can a watch be too thin?” I have a hypothesis: No. A watch cannot be too thin. Spoken like The Dude, “Yeah, well, y’know, that’s just, like, uh, your opinion, man.”
There are plenty of tall watches in the world. Divers make up a bunch of them, followed by tough, outdoor watches, and world travelers armed with GPS and other technology that takes up space. Dive watches can be as much as 14 millimeters tall.
But when a watch’s design goal is to be thin and elegant, no amount of slim is too slim. It’s relatively easy to accomplish a slim watch with a quartz movement: it requires a thin Ronda movement and a battery to match. For a mechanical movement, this becomes more of a challenge. A good example of how hard it can be is the NTH Näcken, where the design goal was a 300M water resistant diver with 11m thick case. In the end, it was only possible to have that water resistance at 11.5mm. For more elegantly styled watches that don’t require the same water resistance, it’s a little easier, but only slightly.
Thinking about it, for a case, crystal and back to have a total thickness of 6ish millimeters, the movement must be about 3 mm thick. That’s an achievement whether the movement is manual, automatic, or even more complicated. For automatics, that would be incredible on its own. But some manufactures have taken thinness as its own quest and made movements where the whole case is three and a half millimeters or thereabouts. The way to do this is by making the caseback act as the mainplate of the movement, making it do duty as both.
The history of watchmaking is one of attempting to make mechanical works of art that practically tell the time, and show off the skill of the maker. Sometimes that’s just through consistently good workmanship of a tool watch, and sometimes, it’s through the attempt of something anyone else might see as madness; The pursuit of thinness for its own sake, with complications worked into increase the height of the accomplishment. Sometimes these take the form of a 1 mm thin solar movement, a 2 hander with sub seconds in manual or automatic, some with date, and for the truly barking mad, minute repeaters and tourbillion, with power reserve. To be fair, at the high end, you’ll pay for thinness as a trait, because it takes so much extra work to accomplish. Thin and complicated are not words that go with budget in watchmaking.
For years, the goal of watchmakers in the 20th century was in making watches smaller in diameter. Early wrist-worn watches were pocketwatches encased in leather (the Wristlet) first used in the Second Boer War, then in World War I, followed by pocket watches with lugs soldered onto them for a ribbon or strap to tie to the wrist. Then, when soldiers came home and continued to wear a watch on the wrist, something that would have been unthinkable earlier, watchmakers began to look into reducing the size of the watch. Watches began to be 24mm wide, and then even 17mm wide, sizes that would be unthinkable for a man to wear today.
One of my grandfathers had a 1949 Bulova Director, a square tonneau case watch in manual wind with sub seconds in a 10k gold filled case. The watch is 25mm wide not including the crown. Today, this is too small for a women’s watch, but at the time, it was solidly a man’s watch. Interestingly, as I look at the movement in the Junghans Meister Driver handwound and the movement in the 1949 Bulova, the jewels, gears, and other details are all in about the same physical locations. 
Nothing had to be moved in to overlap to make the smaller movement, it’s simply an exercise in miniaturization. The case of the Bulova excluding its tall, dual direction convex square crystal is about 5ish millimeters. 
The point is, watchmakers have always taken on challenges whether it’s thickness, miniaturization, complications, or other ways of demonstrating their skill and artistry. Our mission here at WristWatchReview is to highlight this sort of artistry. I want watches to be respected as technological artifacts, tools, and works of art.
Whether it’s Junghans, Piaget, Bulgari, Vacheron Constantin, the Christopher Ward slimline, Torgoen T39 slim, Zenith, or even a Citizen Eco-Drive 1, that’s run by a movement just 1 mm thin, no, there is no such thing as a watch that’s too thin.
