Once known as the “Hobby of the Kings,” coin collecting is a global pastime open to anyone with an appetite for accumulation.

Quarter collectors are watching a small group of historic pieces rocket in value as bidding wars erupt across major shows and online auctions. I see a clear pattern behind the surge: low mintages, key ...

Some quarters that have been circulating for more than 20 years are still worth only face value, but a handful of rare dates and varieties can sell for hundreds or even thousands of dollars. I look at ...