I've had two or three Leica IIIf's including a very nice red dial with self timer (you said IIIG but I checked your ad and it says IIIf) and now have an S2 black dial with 50mm f1.4.
Very different cameras and as nice as the Nikon S2 is I don't use it anywhere as much as I did my IIIf. The little screwmounts feel very refined to me and are a pleasure to shoot with ... the Nikon has never given me that feeling so it gets little use and has become somewhat of a shelf queen!
I don't think think a clean IIIf and 50mm is the same in value as an equally clean S2 and f1.4 though which could explain the lack of interest in your WTT ad!