What's It Made Out Of?

So this is a question I have been pondering for months. The yellow color is indicative of brass, while the copper color is indicative of bronze - at first there was only a little brass coloring, and I thought maybe it was repair work. But the more you grind or sand you realize that the brass coloring is the inherent color of the material.
The fundamental, simplified, version of metallurgy concerning BRASS versus BRONZE is that Brass is copper alloyed with zinc, while Bronze is copper alloyed with tin. WE ALL KNOW THAT ZINC IS WHAT WE USE FOR SACRIFICIAL ANODES IN AN ATTREMPT TO PREVENT THE ELECTROLYTIC CORROSION OF OTHER METALS ON THE BOAT. Common sense would say therefore, since brass is made with zinc (typically around 38%) we should NOT, in general, use it on boats. And that is absolutely correct.
So my hypothesis for the bronze color is that the bearing is in fact brass, but the zinc from the surface is gone, so you get the more bronze coloring, but only on the surface. One alternative explanation is that the material is RED BRASS, which is actually considered a bronze as well - the composition being 85% copper, 5%lead, 5% tin, and 5% zinc (according to one source). While I am in no way an authority, and from my reading I don't think that red brass is as good (or expensive) as silicon bronze, I THINK it is accepted as useable on a boat. Check out www.copper.org if you want some in depth info. Search for bronze and or brass. There is significant conflicting information on the names and percentages of the copper alloys, depending on what site you are on, but this is a topic worth educating yourself. Google, baby, Google!
Further evidence that it is brass is that when we tried to TIG weld it to build up the broken area the metal "exploded" as ,what I think, was the zinc vaporizing (zinc vaporizes at very low temperature - that why it is tough/unpleasant to weld galvanized steel).