I'm living in Holland and I use a program called Spotnet for "Comp Trading" these days. I guess the usage/language is only Dutch.
Years ago (10?) I did some comp-trading with some of the guys here, on this forum, for instance with Hyfi (His famous Bill Bruford comps). Exchanging by US Mail.

Hyfi and others; I see you're still active on this forum. I'm lurking once and a while. Greetings.