I may be a voice from the wilderness (or the dark side) but I say collect Mexican Republic 8 reales coins. Minted off and on from 1823 to 1895 at 14 mints and in circulated condition they are available near spot silver price, except for the keys and some of the early dates. Big beautiful historic silver coins and "not what everyone else collects". Since they were legal tender in the USA until 1857, you could stick to the early dates and call it a US classic collection.