The CG monogram is often mistaken for and referred to by collectors as a dollar sign, albeit a backwards one. Sometime in the 1960s, the circular configuration of backstamps gave way to a more straight text format consisting of PYREX ® in larger letters with model and capacity information in smaller characters above, and MADE IN U. On many pieces, various numbers and sometimes letters are seen in and around the backstamp.

backstamp dating-52backstamp dating-65backstamp dating-10

The backstamp in Fig 2 has a lot of detail: the Spode company name; the country of manufacture; the pattern number S3324; the pattern name and a red workman's mark.

The K following the pattern number is the datemark for 1986.

The Spode company name changed from W T Copeland & Sons Ltd in 1970 when it became Spode.

(Ownership had been out of the Copeland family since the mid-1960s).

The design of #500 series refrigerator storage dishes' lids can help determine their age.

From 1947 until approximately 1959, the lids' tops had longitudinal ridges flanking a smooth middle, and had smooth undersides.

├ A Glossary of Terms ├ Dating Pyrex Kitchenware ├ Pyrex Ware Patterns │├ Pyrex Pattern List │├ Pyrex Pattern Browser │└ Pyrex Pattern Timeline │ ├ Standard Patterns │ └ Non-Standard Patterns ├ Pyrex Opal Ware Shapes ├ Pyrex Model Numbers ├ About Pyrex Item Numbers ├ About Pyrex Colors ├ Pyrex Solid Colors ID Chart ├ Pyrex Promo Accessory ID ├ Vintage Pyrex Advertising ├ Pyrex Catalogs & Brochures ├ Patent Database ├ Videos & Links └ Accessories/Books/Apparel Estimating the age of Pyrex opal glass kitchenware can most often be done by observing a few basic characteristics. Production of opal ware commenced in 1936 after the merger with Mac Beth-Evans Glass Co. The plant there would be used to produce a more durable messware for the military. in a downward curve below forming a broken circle of sorts around the name. No model number or other information was included on the earliest pieces. 1950 or shortly thereafter, the registered trademark symbol "®" was added below the name, the encircling wording became TRADE MARK above the name, with MADE IN U. These appear to be related to either molds or production runs. Patterns The first pieces to have a decorative graphical pattern applied appear to have debuted in 1956.

While colors and styles of decoration reflected consumer tastes at the time of production, the first thing to look at is the backstamp. But the product would not be branded Pyrex until the debut of kitchenware made from it nearly a decade later. New patterns were introduced in keeping with changing tastes, so they can also give clues as to time period.

First introduced in 1938, mainly for the US market, the pattern was in production until the close of the Spode factory in 2009 and is still produced in 2011 under the Spode brand from Portmeirion.