Starburst is one of the most wanted rare Pyrex patterns, but the the Cinderella Serving Casserole almost never turns up for sale.

How can you tell Rare Pyrex?

Use the glass markings, stamps, and logos on the pieces themselves to identify when the glass was produced. The oldest Pyrex markings should be on the bottom of glass pieces and feature Pyrex in all capital letters inside a circle with CG for Corning Glassworks.