Johan,
I picked up Tanack IV-S with 50/2 Tanar and 35/2.8 W Tanar with finder. Camera is gummed up, and lenses were fungus infested, but cleaned up very nicely.
I have noticed, however, that 50mm Tanar focuses to 1.5 feet, coupled to 3 feet only. Must be nice lens to use on micro four thirds. I have to try it on my wife's EP-1. Did you happen to use 35mm Tanar in the past? Both lenses are very well constructed.
Also, do you happen to know, who made Tanar lenses? It seems Tanaka made them themselves, but I am curious.