In that time we hat Microsystem tires. They had an Aqua (20 shore) for damp situations and a H.V for wet. H.V were Aqua with Tamiya cap over it.

All brands today have a very soft tire called like Umido, Aqua and other names...

Full wets are so far only made by Kiss tires who now is using Pitzu Mitzu touring car rain tires mounted over a foam tire.
http://www.kiss-tyres.ch/
Soon I hope to have a fresh set.

If you have facebook, some pics:
https://www.facebook.com/media/set/?...7404651&type=3
https://www.facebook.com/media/set/?...7404651&type=3
https://www.facebook.com/roelof.toom...7726552&type=3