It's a horrible mess. As someone mentioned, some use numeric symbols that I'd expect not to be unique, and while I assume most are unique because everyone uses

It's a horrible mess. As someone mentioned, some use numeric symbols that I'd expect not to be unique, and while I assume most are unique because everyone uses a different format, you will probably have collisions. Even worse is that there seem to be variants (or is it the same stock simply traded on different marketplaces), which may be denominated in the same or a different currency. And getting from one of the symbols to an ISIN and from an ISIN to the symbol is rarely easy. And I'm not sure if an exchange:ticker tuple always maps to exactly one ISIN (and one ISIN can definitely map to multiple exchange:ticket pairs).