The Omega Speedmaster Professional Chronograph. Also known as the Moonwatch. Here it's on a NATO style black band. I've got the bracelet for the watch too, but wanted to see how it looked on something different.
It was certainly the first watch worn on the Moon (Buzz Aldrin's watch; Armstrong's watch was left in the lunar module orbiting the Moon) but serious doubt exists about it being the only watch worn on the Moon. Here's some details about the possible location of the first watch worn on the Moon, long thought to be lost.
Added: Chuck Maddox has written a well researched article about other watch models which have also been worn on the Moon. Read it here.