Superfest! I have a Superfest beer mug actually. They aren’t absolutely unbreakable if you were trying, but they are impervious to pretty much any accidental damage.

The capitalist story was that it was an “innovation of necessity” because people couldn’t afford “normal” glasses. In reality it was just part of the GDR’s philosophy of making the best products they could as locally as possible while reducing waste. They were thin and lightweight but extremely durable. The science involved in making them is a fun read.

As you might suspect, the idea of an affordable glass that didn’t need to be replaced didn’t sell well in capitalist circles and the technology was abandoned after reunification and the plant dismantled to make sure no competitors tried to use it.

It’s one of my go-to examples anytime someone tries to bring up that capitalism fosters innovation, when in reality it does exactly the opposite.

EDIT: It doesn’t look like Superfest specifically, but I imagine there were similar design principles in play.