I remember seeing them at the last Audio Show here in Atlanta (1972?). I could not tell you about their sound, but I do remember I was interested in the line. If I am not mistaken, they compaired favorably with JBL's monitors at the time.
I ran across this link for the Tubaflex Model which I think pre-dates the pair you are looking at. At least it might give you some idea of the Kirksaeter stats. It is in German since the company was in Germany (the new Kirksaeter is in Norway) but is pretty easy to guess what the words mean.
There are very few speakers I would even consider buying (today) from the early 70's. $400.00 seems like a lot of money for a 30+ year old speaker but I have seen JBL L-100's go for as much or more. YMMV