I just got my '69 speedmaster. Should I take it off when I wash my hands? I'm not talking letting flowing water over it, just the mist that may hit it by accident.

 

The only Way to get sure is, go to your AD and let your Watch testing for Waterproofing.
Imho the only Way to go.

 

+1 it's not the age of the watch that will make a difference, if you service it it should be fine. At least of casual watering So to speak

 

If you're worried about getting it wet and damaging it, then you should take it off when washing hands.