How to Date Vintage Pyrex (Years, Backstamps & Shapes)

Wondering how old your Pyrex is? You can usually narrow it to a decade — and often a few years — by combining three clues: the pattern’s production years, the backstamp style, and the shape. Here’s how.

Start with the pattern’s years

This is the single most reliable clue. Each decorated pattern was produced in a known window — Butterprint ran from 1957 to 1968, for example. Identify the pattern first (see How to Identify Vintage Pyrex), then check its page in our Pattern Database for the production years. That alone usually places your piece within a decade.

Read the backstamp

Corning’s Pyrex marking changed over the years, so the stamp on the bottom is a useful secondary clue. In general, earlier opalware pieces carry more detailed marks, and over time the logo and wording were simplified. Look for “Made in USA” (standard on US-made vintage pieces) and the model number. The exact logo style — and whether the mark is a stamp versus a later molded-in mark — helps confirm the era suggested by the pattern.

Use the shape as a tie-breaker

Some shapes have known introduction dates. The tab-handled “Cinderella” bowls and casseroles (with the pour spout and grab handle) arrived in the late 1950s, so a Cinderella piece won’t predate that. Matching the shape number against our Shapes & Model Numbers guide can confirm whether a form fits the pattern’s years.

A note on clear Pyrex

Clear glass Pyrex ovenware sometimes carries different markings than the decorated opalware most collectors focus on. If you have clear pieces, date them by their logo style and stampings rather than a printed pattern.

Putting it together

Pattern years give you the window, the backstamp confirms the era, and the shape rules out anything too early. Combine all three and you’ll have a confident estimate. Once you know the age and pattern, check the value on its pattern page — and see which designs are the most valuable Pyrex patterns.

Frequently asked questions

How can I tell how old my Pyrex is?

Start with the pattern, which was made in a known range of years, then confirm with the backstamp style and the shape. The Cinderella tab-handled forms, for instance, didn’t appear until the late 1950s.

What does the backstamp tell me?

It confirms authenticity and helps date the piece. Vintage US pieces typically read ‘Pyrex’ with ‘Made in USA’ and a model number; the logo style was simplified over the decades, which helps place the era.

Does the number on the bottom tell the year?

No — the three-digit number is the shape/size code, not a date. To date a piece, use the pattern’s production years plus the backstamp and shape together.