I recognize this watch from many years ago. It was for sale on eBay, along with a few other intriguing examples. I am inclined to believe that the dial is not original. To me, the signature does not look correct. The font is neither the typical Fluckiger style, nor what I would expect from Stern Freres. Further, the two-tone yellow design is highly atypical. I do not recall seeing another original 13ZN dial quite like it before. Additionally, the hour and minute hands are too short, and the chronograph second hand is incorrect. Also, I disagree that the case looks unpolished. Please compare with the example below.
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