Pyrex Collective II

I found this 6” pie plate at my neighborhood Goodwill a few days ago. It has the original Pyrex backstamp and has air bubbles in the glass (which you can see in the photo).  It also has a scratch, so I put it back on the shelf a couple times before finally deciding to buy it. When I got home, I held it up to the light, and in the backstamp it reads “May 27, 1919.”