Here are a few resources which I find very helpful for researching information on coins and tokens:
- Numista: A very comprehensive resource for coins from all around the world. Now also featuring Tokens (be sure to search in Exonumia) and Banknotes: https://en.numista.com/
- Token Catalog: A very good reference for tokens. For the majority of tokens I have been able to find ANY online reference for, the majority are listed either on Numista or Token Catalog: https://tokencatalog.com/
- The NGC World Coin Price Guide. A handy way to get a ballpark figure for what various coins are worth. Just under the header is a link to a US coin price guide: https://www.ngccoin.com/price-guide/world/
- Coin Project is a very extensive site for ancient coins: http://coinproject.com/
- Tesorillo is another useful ancient coin site with a handy reference of late Roman bronzes: https://www.tesorillo.com/