Well -- I think the thrift store knew that they were dealing with some of the nicest high end American made speakers. They were priced @ 300$. I don't have a supporting cast for this caliber of equipment (I'm running a sony sound bar in my living room) but I knew, even without a google, that I had some nice quality speakers on hand.
Based on what Audiogon has listed in the online blue book, $300 is about full blown retail for these. The Model 2 was released in 1977 at a cost of $990.
They released subsequent models and added an a, b, c etc. to the end.