With 10 models to choose from the CuSn8 Series is made of high quality German CuSn8 Bronze. CuSn8 is the chemical composition of the metal. It is rose gold in color.  It is made usually of 7.5-8% Tin, approx. 92% copper and around 0.30% phosphorus. This mix is highly sought after due to its low amount of impurities, and because it hardly gets any reaction from oxygen. This, in turn, makes the material all the more resistant to all possible forms of corrosion.  Your watch may and likely will get a slight Patina over time (much slower rate than lower quality bronze) but the high quality bronze we are using is resistant to corrosion.  You can on occasion polish your watch to get rid of any patina that occurs. CuSn8 Bronze is the highest quality bronze for watch making.