Those Blue Book values are either wrong, or for one speaker only. The military BX's sold those when new, and a pair in there was $579, so I'm thinking MSRP on the outside may have been $550/speaker.
In any event they were absolutely terrible. 15" ported woofer, in a tall cabinet that was so flimsy in construction, you could rock it back and forth with your pinky. The SM-80 8" two-way wasn't bad, as was the 10" three-way, the SM-100. They cheaped out on the cabinet bracing (among a bunch of other things) when they got to the SM-120 and 150, and it sounded like it.
Thor may be right about that SM series being good rock speakers. Distorted rock would be helpful.
Toasted Almond