A quick question about a Sea Dweller.

[wintermute]

Hello!

Well, my dad managed to buy a Sea Dweller relatively cheap on eBay. He's got a couple already (he's a bit of an obsessive collecter) and he's given it to me a University graduation present (and for getting into Med school, kinda) and I have a couple of questions.

It runs a little fast, which is nothing out of the ordinary and that should be taken care of with a service. However the little button (I'm guessing it's made out of pearl) on the 12 o'clock position of the bezel has fallen out (hence the cheaper price along with a couple of superficial scratches on the bezel itself).

How much is it to get a new one fitted? Will it need a new entire bezel. If so how much do they cost?

Also I'm not sure how old it is (it's not the deepsea) when did Rolex start etching the logo into the crystal above the "Swiss made"? I think my dad said it was model 1660, does that help?

Lastly to any divers out there: Why does the bezel show how much time you've used up and not how much you have left? When diving I guess you'd need to constantly minus time spent against total air time. If they swapped the 10 and 50 around (with 40 and 20) then wouldn't it show how much you have left? I know it's a professional watch, so there must be a good reason; but why?

Thanks!