I might have generalized then. It’s maybe something that we had only in the south (aka the broc à eau area). We also used it to check our age of course.
As the article said Duralex was the brand use by a large number of school cantinas in France. Inside of each glass there’s a small number used by the brand to identify the mold used for the creation of the glass. For kids that was a way to decide who is going to fetch the water for the table (smaller number or higher number of the table).
That’s why the CE is holding his glass like that in the guardian article.
Beside the nostalgia i think a lot of people support them because it’s a SCOP (the majority of the capital of the company is owned by the employees) [1] and it’s nice to see that another kind of company is possible.
[0]: https://m.youtube.com/watch?v=ni-1x5Esa_o