Hello
It was in fact a factory option that cost the same like the convertible upgrade.
It is simple a modificatet Steelroof witch uses normal Glas.
The complete convertible top had to be removed to put the Hardtop on.
I know a Porsche dealer who is storing the softtop for a Hardtop convertible since the car was delivered. Guess the car didn´t have very much milage
WST Wiesmann also offered a Hardtop but made from Glasfibre/Aluminium composite. This idear and look was duplicatet by Strossek as well.
Bauer once showed a clever hardwindow version.
Had seen it on there inhouse fair but never heard if they sold it. Maybe they had to much work with the Mercedes and BMW´s.
Grüsse,
Roland