I’m sure you’re referring to these Opalithplättchen, aren’t you?

Impressive that you could remember the name. I’m German and had to look it up since I never heard about Opalith before.

Exactly! Bicycle pedals have a left-hand thread on the left-hand side and “normal” threads on the right-hand side.

In the plumbing sector, left-hand threads are used whenever two pipe ends need to be connected that cannot be rotated. The connector is then equipped with a left-hand and right-hand thread and can therefore easily be screwed between them.

So it’s not just typical for Nordic countries, but depends on the application.

VPNs aren’t working unfortunately, at least if you’re not logged in. They completely block the site when you’re trying to access reddit via VPN. This is a VPN related forum where this is discussed.

Here is the original source with better resolution.

Looks like a can of Tuborg beer.