Eta movements that are equipped with a hack, usually hack the balance wheel, not the train wheels. I suspect this Tissot movement is the same. Some watches hack the fourth wheel which carries the seconds hand. Why does that matter. It matters because, on a watch that hacks the fourth wheel, the normal “lash” in the train wheels you would expect as you set the hands, is eliminated. On a watch that hacks the balance wheel, the lash in the train is still there. Why don’t you go to a Tissot dealer and check out his inventory of Tissot POWERMATIC 80 watches to see whether your watch is unique. This phenomenon is hardly likely to throw your watch out by a second as the lash will be taken up once you return the stem to the run position.
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