I think this envelope got returned to Frieder, because it was included in another envelope and they both had cancellation marks. It's a beauty. And I love the stamps on the back as well.
The card is a cut up painting on paper, from the early 90's. I haven't seen the other ones of the series, it would be interesting, but this one sure can stand on its own. Thank you Frieder, I was so happy to get this first mail from you!