Anyone have any info on RTR Series IV C Speakers

I purchased a pair recently at the local thrift store.
Really like their sound and would like to get more info on them. Anything provided would be helpful.
I've heard those are supposed to be pretty cool. I think they use the same peerless cone tweeter used by Sonab of Sweden in the 70's... don't know if that helps at all.
Every bit helps.
They do sound very good especially when I consider they are 25 years old. 12 inch woofer really produces a lot of tight bass.