I found one website late last night that references Elvis buying a second Jetstar because the first was "subject an to FBI investigation that wasn't resolved until after his death," but no further details on registration or disposition of either of the Jetstars to tell which was which, but I'm guessing that, if provenance holds, N440RM is the one that was in the legal battle as I found this when looking up the registration -
https://www.planelogger.com/Aircraft/Re ... 0RM/755010However, this history is somewhat interesting because it doesn't have a date of return, only that it was in the possession of Air Capital in 1981 (about the right timing), but no information of the airplane in the Elvis estate or anything in the intervening years. Supposedly the aircraft was purchased ca. 1975 by Elvis so it'd be in that timeframe that is "unknown".
I also found out that the current auctioneers of the airplane are the same ones that auctioned it off in 2008, only the name of the company has changed from Kruse to GWS.
Here's another thread with what appears to be more information -
https://discussions.flightaware.com/post131369.htmlI'm not discounting that this isn't Elvis's airplane as there are some references to him having 2 Jetstars, but it just seems there's too much information on this airplane that doesn't quite add up and no real proof anywhere provided that this was in fact "his" Jetstar.