A second aircraft ZK-GIM2 , c/n 129S9120104 is with Kester Holdings of Auckland.
And the winner is :-
Well :- an early Anonymous mentioned a "High performance glider wing". Afraid the Sinus is not [in my view] in the high performance class.
Henry almost got it with the type and gave us the two Sinus registrations. Shame about the 503 reference.
Wayne started off ok but then removed his comments.
And then - [by the hair of my chinie chin chin] - another Anonymous gives all the details required.
So feeling extra generous tonight :- If Henry & the final Anonymous would like to send their snail mail address to me at firstname.lastname@example.org I will flick a fish in your direction.