Today my Delco Carousel IV-A Display Unit arrived from the US. It came in a much better shape than I expected it to.
The switches provide are very springy and provide a satisfying clicking sound when pressed. The thumb-wheel and the mode and test selector all provide the same clicks, you are always sure, what state is currently selected.
Judging from the accompanying Removed Parts Tag (see figure 2) the unit was removed for modification. I assume to replace it with a more modern FMC. Nicely this tag also reports the aircraft registration number of the plane it was removed from, N488EV, An Evergreen International Airlines aircraft. This Boeing 747-200 appears to have first flown for Lufthansa in June 1985 (according to planespotters) under the registration D-ABZA and was later, in 1993, modified to a Cargo plane for Lufthansa Cargo. In 2005 it was sold to Evergreen Internationl Airlines (around the same date the CIVA was removed) and continued to fly in their service until June 2012.
On airliners.net I found a picture of the unit still mounted in the cockpit (taken early 2003). It is nice that the unit made it back to Germany after 10 years in storage in the US, having spent at least 20 years flying exclusively for a German airline.
This story seems absolutely plausible since the unit still wears a Lufthansa inventory sticker on its back (see figure 3). It was last maintained in July 2004 by Northrop Grumman, one year prior to removal from the plane.
As next steps I will try to dig up some more information, ideally even some wiring diagrams. Although I unfortunately did not have any luck in this regard so far. I will post anything interesting I can come up with. Also I will post some pictures of the internals of the device.