Haven't got a clue, it was a top-secret project. But he was really sweet and a true gentleman.
Only problem was that I kept stubbing my toes against his invisible pilot helmet now and then; I couldn't see the darned thing. And of course he kept leaving it all over the place. Very impractical.
The situation is getting worse ! I've just noticed that two old Monogram kits have been re-released under the Revell label, the 'Visible' B17 and 'visible' Mustang, each with a clear fuselage half. It makes the model look like it's turning invisible.......