This is also true for our birds. I have been a jeweler for most of my life, involved in the actual metalsmith trade, that is the actual making ofthe jewelry as a goldsmith, silversmith, pewter manufacturer, and shop owner. I have worked with metals of all kinds. Iron, steel, copper, bronze, brass, nickel, tin, gold, and silver are not toxic metals. It is inexpensive and used to make castings of almost any item imaginable .
Pot metal is like a recipe melted in a pot containing combinations of tin, antimony and lead.
This is then poured into molds to make jewelry and other small metal items. The metal is then plated or painted to look like gold or silver. My advice is not to let your bird chew on any metal you can't identify. Don't try to guess. Don't take a chance and be wrong.