The Tissot Forum has some real experts. They may know more. But it is not at all unusual for crowns to be replaced. The gaskets in crowns are almost impossible to get out without some scratching and any scratching can cause water resistance problems. Most watchmakers do not have access to OEM Tissot crowns but rather have a generous supply of generics they use for replacement. So you get a generic if the watch has been serviced. Indeed, an original crown CAN mean the watch has never been serviced - a bad sign. So generic crowns are, to me, a good sign!
Other than that, the crystal needs a polish or replacement but the watch looks good. I hope you plan on having a service.
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