Pyrex dishes also hide a little secret code: Many contain a three- or four-digit number that corresponds to a specific dish. A series of Mixing Bowls will feature 401 (1.5 pint), 402 (1.5 quart), 403 (2.5 quart), 404 (4 quart). The iconic two-quart green-and-white casserole dish is a 232.

How can I tell how old my Pyrex is?

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.

What is the rarest pattern of Pyrex?

Pretty much everyone in the Pyrex collecting community agrees that Lucky in Love is the rarest Pyrex pattern ever released. Lucky in Love is an elusive print that dates to 1959 and only appeared on one-quart round casserole dishes.