Help with Pyrex 344 3 Quart Glass Bowl?

[David Hunter]

Hello,
I am trying to find a Pyrex 344 3 quart clear glass bowl. There are usually several on eBay but how do I know which ones are made from borosilicate glass and which ones are not? Are there markings I need to look out for? From what I've read, the new Pyrex bowls are not made from borosilicate glass and are not oven safe. I have been using a vintage Pryex 344 to bake bread in the oven at 500º for years now and I would like to find a good, clean, minty, back-up bowl. I just want to be sure I'm getting a true borosilicate Pyrex 344. Thank you.

[Doug D.]

The shape appears to have been discontinued after 1981 (the 343 earlier, probably around 1975). The switch of US-made clear Pyrex from borosilicate to tempered soda lime appears to have taken place much earlier than many are lead to believe. It is often repeated that the change was made by World Kitchen in 1998 as a cost-cutting measure. The early 1950s has been confirmed by more official sources, however. Pyrex licensees in other countries continued to use borosilicate long after that.

This post has been updated to correct earlier incorrect information..