RADO Coupole - advertised as first "caseless" watch, ca. 1990

For your reference...
The watch is 30 mm in diameter and my wrist is 6.25 inches or 16.5 cm. Back in Switzerland when wearing a business shirt, it happened to me to think I forgot the watch. One day, I even went back home without checking under the sleeve. I felt pretty dumb when realizing that I had just walked the "Coupole" to the tram station and back thinking I was wearing nothing. Small watches wear great!