Has anyone ever seen or used one these in the past ?

I just ran across one of these ...

Hi Dan01
The EX 20 was the module version of the MK1 S III synthesiser from the Mid 80s, and from what I remember could produce some cracking sounds.
Here is a link which gives a few more details http://tinyurl.com/yvvssz just scroll down to the MK1 S III (It’s translated from French I think)
Hope this helps

Bill