Collectors' questions span everything from selling and grading coins to famous U.S. coin designs and Mint policy.

Here are 20 rare state quarters worth additional value, according to Gainesville Coins, USA CoinBook and PCGS.

There’s something to be said for collecting old coins. Some people do it for the fun of it or to have a cool story to tell. Others do it in hopes of making a profit. Unfortunately, not everyone’s ...