There have been thinner watches and thinner movements – the thinnest quartz Delirium was just 0.95mm thick and is, I believe, the thinnest watch ever made, and in the 1920s Vacheron produced the caliber 10726, which was a pocket watch movement, just 0.90mm thick. Both the Delirium and the Vacheron caliber, however, were extremely fragile and
link not very practical (Vacheron only made three
link caliber 10726 movements and then gave
link it up).