After all these years, I finally get around to Googling them. Vintage 1973, according to Radiomuseum. Can't find the original price, but I found the spec sheet in German.
And then there's this Youtube, where they really, really sound awful.
https://m.youtube.com/watch?v=30lVg7HsbEg
And then there's this Youtube, where they really, really sound awful.
https://m.youtube.com/watch?v=30lVg7HsbEg