Bronze is a highly machinable copper alloy that ensures the highest quality standards of case construction in your new Vostok-Europe watch. As copper and tin are key components of this alloy's construction, the final composite metal is subject to oxidation. As such, after a few weeks of wear, these watches will develop a "patina." This patina can produce a variety of colors on the metal surface and, in so doing, make each bronze Vostok-Europe piece a unique item with distinct case colorization that will be the personal reflection of the wearer. However, should you prefer the absence of a patina on your watch, the case can be polished with any professional bronze polishing paste.