He references this FAQ from the Corning Museum of Glass (CMOG):
> The short answer is that the change from upper to lower case signified a re-branding of the trademark Pyrex® in the late 1970s but is not a conclusive way to determine, historically, what type of glass formulation the product is made from.
* https://www.youtube.com/watch?v=2DKasz4xFC0
He references this FAQ from the Corning Museum of Glass (CMOG):
> The short answer is that the change from upper to lower case signified a re-branding of the trademark Pyrex® in the late 1970s but is not a conclusive way to determine, historically, what type of glass formulation the product is made from.
* https://libanswers.cmog.org/faq/398431