Even on brass articles, Brasso should be used with caution. As said, it works by abrading the metal, removing the surface layer of oxide plus whatever stuck-on crud there might be. The abrasive nature of the polish is obvious if you use it on a coin (of whatever metal) because it wears down the design and there's something to compare the wear to. But if you polish something with a smooth surface, such as a motor car lamp or a trumpet, you are still removing the surface. Eventually you will wear through the metal.
When I was a lad I had a Saturday job at a mechanic's garage where old cars were restored. His speciality was pre-1920 cars, which used to have huge amounts of brass, plus lights and other accoutrements that were bolted onto the car rather than being integrated into its design as such elements tend to be on modern cars. These cars were already 80-odd years old and had been polished for that whole time. The guy I worked for was insistent that I (or anyone else) should only use Brasso on the lamps as a preliminary polish on lamps that had sat getting cruddy for years. For lamps that were already well cared for but were just a bit dirty, soap, water, clean dry towels and plenty of patience were the required tools.
