Regular watches can become interesting for many reasons and this 15200 model has developed a nice "sand" tropical patina. The occurrence of a silver dial developing such a patina is very unlikely. The watch is good overall with 11 links on its 78350 bracelet. 
 
Details:
 
Brand: Rolex
Model: Date
Reference: 15200
Year: 1989
Material: Stainless Steel
Dimensions:  34mm
Crystal:  Sapphire Crystal
Movement: Automatic Cal 3135
Bracelet/Strap: 78350 Bracelet
Box/Papers: No/No