So that is what those things were I saw when I briefly joined De Electronenclub ('The Electrons Club' in Dutch) in the early 70's. I was around 7 years old and never got to do much with these but the concept fascinated me to no end. Later I got to fiddle with similar although more complex Fischertechnik blocks at a friend of mine (hey Erik!) but those were wired together where these things worked like magnetic dominoes.

I assume it was the Braun version I played with given that this was the Netherlands.