Patek Philippe Calatrava 3420

Hi All,

I'd be grateful if anyone in the know could share some advice about a recent purchase I made:

https://www.gioielleriafrollo.it/prodotto/patek-philippe-calatrava/

The watch was sold to me as unpolished with original dial, plexiglass, crown etc. On inspection it looked correct to me, but I am no expert and admittedly fell in love with the watch and bought it rather impulsively after negotiating a good price in store after seeing how much interest it was receiving on Chrono24 at a higher price.

When I got it home I noticed under direct sunlight and looking very closely, that there is a very slight mark around the dial edge between approx. 13 to 3 o'clock. It is barely noticeable at all, but now that I know it's there I'm keen to understand what it is, what caused it and whether it's something I should be concerned about.

The mark on the dial is visible in the 2nd photo attached (IMG_1549-scaled.jpeg), and also in the link above when zooming in.

Would anyone know what that mark is and whether it could be easily removed, or is best to leave it as it is? I'm assuming it's slight moisture damage of some sort. The mechanism looks to be clean, at least to my untrained eyes.

If anyone else has any other advice about the overall condition that would be much appreciated.

Many thanks!

... and here is a more zoomed in image of the dial with a red line to highlight the approx area where the mark appears to bleed onto the dial.