YSK how to identify the older, safer 'PYREX' glass from the newer, "exploding" 'pyrex' glass cookware.

A couple of decades ago, Corning sold the Pyrex brand name to another company called World Kitchen. Unfortunately, they changed the formula for the glass, and the new dishes have a reputation for exploding. (Not just breaking or cracking, but actually exploding in the microwave or convection oven.)

So, how can you tell whether you have older or newer Pyrex? From the website Frugalista Files:

According to Wikipedia, Corning's responsibility extends to this formality:

When trademarked as PYREX® (all UPPER CASE LETTERS plus, in the USA, a trademark notice comprising a capital R in a circle) the trademark includes clear, low-thermal-expansion borosilicate glass used for laboratory glassware and kitchenware, plus other kitchenware including opaque tempered high-thermal-expansion soda-lime glass, pyroceram, stoneware, and metal items See. e.g.,http://ift.tt/2jFLSvC. European trademark usage differs from American and the encircled "R" is not present on European PYREX items.

When trademarked as pyrex® (all lower case letters plus a trademark notice comprising a capital R in a circle) the trademark includes clear tempered high-thermal-expansion soda-lime glass kitchenware, plus other non-glass kitchenware, made by World Kitchen. See, e.g.,http://ift.tt/2jENJ43

So, in short, look for the trademark in ALL UPPERCASE LETTERS.

I checked mine, and it looks like I have about half old, and half new. But now I know what to look for when scouring the thrift stores to replace by cookware.