Hi - I recently acquired a 1970 Tissot Seastar auto that looks very nice and is probably worth putting a few extra dollars into but it's got a problem that maybe some of you more experienced wrists may have seen before. It winds nicely and once running the seconds tick off in perfect time, but the minute hand does not move in proper sync. It seems to behave different at different parts of the dial but it only moves on average about 6 minutes for every 10 revs of the second hand. Is this just indicative of a dirty or poorly lubed movement or does it sound like something broken inside? I'm hoping a standard servicing will bring it back to proper life but maybe somebody has an idea what I'm up against?