Yes, this is a bit of watch-geek indulgence, but some of us just need to know. Here is a chronology of the Moon Watch caseback design. It matters as the Moon Watch is most likely my next watch and I need to know its vintage. The Omega Speedmaster was the first watch worn on the moon. In fact, sticking with Chuck Maddox's site, he wrote this invaluable guide to watches worn on the moon. Yes, it's very geeky, but it's an important article about important stuff.