That plate is on a red Ghibli S now so stuck with the brand. From memory both cars are ex ADG so that's a possibility as to the call to make. If it is then strange that they did not retail it but it must be miles I guess.
I presume we will now enter a phase where most cars get leggy and tired and values drop like this and others that are rarely used hold relatively high prices; i.e. into 4200/GS differential pricing depending on miles.
My GTS is now over 40,000 miles so is probably past the point of preserving it's value. I am as well continuing to drive it over the next few years and accept that it's value at 70/80,000 miles is not a lot.
Part of the value drop might be the fact that the design is now beginning to look old. I still like it and it gets very positive comments but I do wonder if the GranTurismo shape will age less well than, say, a DB9? Not sure about this but it's worth asking.