I posted this in the Omega section, but others may find it useful too:
Those UPO bezels can be a b*tch to get off....here's an easy and cheap way. You'll need a hockey puck (about $2), a hole saw (1 1/2"), a drill, a drill bit (size doesnt really matter), and a hand saw. Here we go:
1. Take the hockey puck and your drill bit, then drill a hole straight thru the center of the puck
2. Get your hole saw on the drill and start running it thru the bit hole you just made. Get as far as you can from one side, then flip the puck over and repeat until you've removed the center of the puck with your hole saw. You should now have a hockey puck donut.
3. Take your hand saw and cut out about 1" from the puck so you no longer have a donut puck, but more like a "C" puck and you're done
Now to use it, place it on your bezel, squeeze hard, pull straight up off the watch, and twist the opposite way the bezel rotates and your bezel will come right off. You have to be sure to squeeze, pull, and twist all at once or else it won't work, but its far from difficult. Here is what it should look like: