Usually what you see is what you get, but every now and then, a truly valuable piece is tucked behind something innocuous -- or sitting right in front -- on a shelf in a thrift store. That glass ...

but not all etched glass is alike. At first glance, it can be difficult to tell true crystal from cut glass. Follow along for our best tips on how to spot the difference between the two.

A woman with long hair holds a glass bowl, examining it to determine whether to purchase it. - Galina Zhigalova/Getty Images ...