Kit Kat Dark are not available in Switzerland and I don't think they are available in the US any longer. This is an excellent candy bar and is probably my favorite. It was voted Product of the Year in 2008 in the Chocolate Confectionery Category of the Consumer Survey of Product Innovation.
The Nestle site has information on the history of Kit Kats. Did you know the packages used to be blue? I learned that a special formula is used in Malaysia, where they make the Kit Kats sold in warm climates. That might explain why the Kit Kats I've had in Malaysia are almost as bad as Dubliner cheese.