They're uncommon. Uncommon enough that they get little attention. I lived with a new pair on a new Sansui 7070 for a while in my early teens(circa 1977). I'd love to find a pair close to home. The low bass output for an 8 inch 2-way speaker is quite impressive. For their time period(and my memory of them), they were very smooth, and well balanced speakers. Of course i have a soft spot for many of the BA/EPI smaller 2-way systems. But, the Jennings have some sentiment for me as well.
Those are well worthy of restoration, and if they're working, just the K 010DT tweeters are probably worth his asking. The foam for the passive on the back might be tricky to source, and i'm sure the foams around the tweeters will be a trick, but not impossible to have reproduced.
Although they were born on the west coast, i think they have more of what would be considered an east coast flavor.