Back in the early scramble to make IBM clones companies used all kinds of propriatory "non-standard" cards and interfaces to add stuff to their motherboards. Wyse, among others, comes to mind. (Of course Compaq still does.)
Some years ago I found a full length card that looked identical to a Zorro card. Turned out it added ports and ram to a very specific PC. C= was not the only operation to use a 100 pin edge conector.
