For those people of a doubting nature let me cast some light here.
Splatcat is the TT id of my girlfriend. I have been in Munich nearly 7 years. She has for most of that time commuted from London and now lives in Zürich, where I will be moving to shortly (see my post to rent my flat). I guess in the past three years she has had better things to do than spend her time on TT commenting about aircraft history and military memorabilia.
The prop is 100% genuine. Probably the most convincing evidence I can offer is the person who is selling it. My girlfriend is Mike Spence's youngest daughter (see OP). Her dad flies, her brother flies out of Iraq at the moment and her nephew is just about to start his commercial licence. They are a family of pilots and Mike still owns a Hanger so it is not really surprising that he sometimes gets given interesting things like this propeller.
This prop was given to us for our apartment in Munich (where it currently is sitting on top of our bookcase), before Mike gave us an already restored Tiger Moth prop that now hangs in our lounge (that is the restored prop in the photo link). So instead of having the gemini prop doing nothing we have agreed with Mike to sell it. What we get for it is going to Mike who despite being well over 80 still flies regularly and goes out for a Sunday burn on his Motorbike.
This is a genuine offer for a really interesting piece of aviation history. The fact is has past through Mikes hands I think makes it even more so as the guy is a legend amongst the flying fraternity of South Africa. I can remember a few years ago he got myself and the missus slots to go up with the air display team the Sasol Tigers...
http://www.capetown.dj/photo/AirShow/Sasol...SasolTigers.htm...As we finished the flight and signed the log book one of the pilots noticed that my girlfriends last name was Spence and after putting two and two together and telling the rest of the team was over the moon to have been able to take Mike's daughter up for a spin.
Anyway if the condition of the prop and the story of it does not convince you of it's authenticity then I guess nothing will.