The one used on In Through the Out Door belonged to Benny Andersson of ABBA and was in Polar Studios when Led Zeppelin recorded there. John Paul Jones soon after got his own.
I don't know what happened to the Led Zep one, but the Benny Andersson one was being refurbished a little while ago. The guy doing the work told me it still has the patches set up by both Benny Andersson and John Paul Jones.
The Electone organ aspect was curious, as MC mentioned. I think Yamaha got their organ division to design polysynths. As I recall there are a couple of slightly different case designs for the GX-1, one of them labelled more as an organ than the other (there are also two colours, black, and white). I believe the EX-1 and EX-2 also use GX-1 technology.
A guy called Flametop Fred on another forum raised the point that several Yamaha organs used their synth technology. That seems to be true but I think it's less exciting than it seems. A few people were hoping to get a cheap CS80 equivalent that way, including me. It is true that you can be lucky enough to get a good sounding instrument for very little money that way, and Flametop Fred posted some very nice sounding Electone demos on YouTube, but the GX-1, CS80 and so forth scored because of their playability rather than just their sound.
Incidentally the solo parts on Wendy Carlos' performance of the Fifth Brandenberg are an Electone E-5, which did things the Moog Modular wasn't at that time capable of.
There's a story on the net of a guy who bought a very cheap GX-1 from an organ teacher who'd acquired it after a Yamaha demo concert. Maybe the only time that will happen, but you never know.
Websites: http://musicbysweep.com and http://theSynthiMusicSite.infinite9ths.com