Here's info I found on Reddit that is informative.

What I found with most thrift stores is they may spot the unusual pieces coming in and put it in their auction sites so that is good place to check also. But a lot of times it makes it to the floor of your local thrift store. Garage sales maybe but that can be time consuming with the distance traveled.

Kitchenware Niche Feature: Pyrex, Fire-King, and You. from Flipping


Here's a good video on cleaning pyrex bowls!

Video Transcript

hi everyone is judge all well i recorded this video once and I didn't realize when I was cleaning this bowl that my hair was in front of the camera so that's all you could see so I'm gonna try it again um I want to start by saying I am no way endorsed by these companies are paid or anything like that this is solely my opinion and I also realize there are other ways to clean you know the pyrex bowls on this tutorial is just to show you how to clean on the utensil marks off of vintage pyrex bowls and this is what I do and what I use so now that the ball is ninety percent clean you can go back to my venture stripped all video number 92 see the condition before I touched it but i'm going to go ahead and show you what i use so what I use is a product called peak and it comes in a box like this i ordered it off of amazon here in the states it's kind of hard to get at least for me in my area so i had to work off amazon but you're in the UK is where it's made you may be able to find in your local store it comes in a tube like this it also a tube like this it also comes in a can I think next time i'll buy the can because I'm going through this pipe fast it's just like a tube of toothpaste and what I do is I take a dishcloth it could be white or drive trying to both ways and it works either way and you just put a little like this on your dish cloth and rub it takes a lot of elbow grease I won't lie it takes me a while but eventually you can get about probably about ninety percent of your marks off the bowl so I'm go ahead and give it a shot see if it works for you and yeah let me know if it works for you I'd be happy to hear all your results so on thank you so much for watching I know it was quick i'm so sorry that my first video don't work out but i like that if you can go back to my adventure stripped all number 9 you can see what it looked like before I was able to get all the marks off here so thank you so much for watching please like this video comment and if you haven't already subscribe thanks so much have a good day right