Well, thank you all for your comments and suggestions, I will take the risk and approve the watch. FYI, Andrew answered me that this morning after I challenged him on some of you having bought a NOOB and case screws seem to be bronze :
" We are selling the same watch. So there isn’t any issues at all. Sometimes the chemical oxidation can spread to the screws top surface and that is a little misleading but I can ensure you that screws are coated to match color of the watch "
To be very honest, I love the watch and I will give him credit, my only concern is how long will the coating last ( if it is indeed coating ! ), especially taking into consideration that I will be using some vinegar fumes, or lemon etc....
TBK , I will contact you in PM for some extra info on how to clean the watch if you do not matter