You could try Acoustat ESL's. People do manage to restore them. You'll get pretty severe head in vice syndrome. But they are very nice within that vice. Here are some model Two's which I have owned.
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You could look for more oddball ESL's like Beveridges.
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Or some KLH 9 speakers.
Or Dayton-Wright XG-8s or XG-10s which were contained within mylar bag holding sulfur hexafluoride gas. The gas had a different speed of sound making the speaker acoustically larger and let it run higher voltages so it was an unusual ESL in that it had good bass and was fairly efficient. Of course that is the most potent greenhouse gas known.
You might try some of the early Martin-Logan speakers in the CLS line. They were a single curved panel. Not much bass, couldn't play loud, not very efficient. For music not needing much below 100 hz they were pretty special.
You could look for old Infinity speakers made by Arnie Nudell. They look something like big panels, but have conventional woofers with his own type drivers for midranges and tweeters. RS models I'm thinking of in this case.
The old Apogee ribbons are very good speakers. Make sure you have an amp that doesn't mind a one or two ohm load. Classe amps were the go to pick for those, but other big iron amps would work with them. I'd think good class D amps would be okay, but haven't seen or heard such a combination.
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The only old box speakers that would be of interest in my opinion might be some of the big horns from Klipsch or Altec or similar.