Here is an auction on eBay.com likely to raise some interest...
18 Duke Ellington live & rehearsal reels owned by Irving Mills RARE Ellingtonia
"Lot of 18 reel to reel tapes of mostly Duke Ellington live performances, unissued studio tracks, and rehearsals along with a few tapes of jazz festivals (Newport, for example). These reels were obtained several years ago from someone who had purchased a storage unit that belonged to a long time reel to reel collector & enthusiast. There were a large number of Ellington reels in the unit (maybe 50-60 in all), but these were the only ones I received. At least one tape has a short letter to "Irv" adhered to it (see photos) and at least two tapes contain personal messages to an Irv/Irving, including one from long time Ellington horn player Harry Carney who mentions an interview "Irv" is going to conduct with Freddie Jenkins in the near future. All this combined with the location in which the tapes were found (near Palm Springs) seams to strongly imply these tapes belonged to early Ellington manager & discoverer Irving Mills, possibly given by friends as gifts over the years evidenced by the personal messages. I have not tested every tape nor do I wish to because, unfortunately, they are not in the best of shape. The Newport tapes in particular are in very rough shape, while the Ellington tapes seem to be better kept. I've listened through several Rainbow Grill tapes and they sound decent, possibly even good to very good. The few tapes tested all had the proper reels in their boxes, but as they are not all tested to confirm these are being sold AS-IS and to be used as music memorabilia or as reusable media.
I recorded samples of the few reels tested (including the Carney message) which can be provided as proof of authenticity if needed, as well as the remaining index photos as eBay only allows for 12 photos in a listing."
I must check what is known to exist elsewhere of the Ellington material before the auction ends. Hope these find a home among the Ellington fraternity. Happy bidding!