The chemical symbol is Al. It is a light, soft metal. It is easy to process and, in theory, has excellent corrosion resistance due to the oxide film that forms on its surface. The aluminum watch released by Vacheron Constantin in the 1940s achieved an ultra-lightweight weight of just 19.16 grams by using aluminum for the case, dial, base plate, and bridge. In recent years, Richard Mille has attracted attention by using AruSic, a composite alloy of aluminum, silicon, and carbon, for its watch cases. However, today, there are only a handful of watches with aluminum cases.