The couple of decades thing has really thrown me ! Until I read that, I was going to offer the roof of the wheel bay of a P47, but that dosen't fit the time span. So, if a couple of decades, it must be a 1950's kite?
Woo! And even Hoo!! I got one right. Sadly, I'm not in a position to add a pic to this thread (plus I cheated on my guess - Googled "1959 three aircraft built" and came up with the X-15...once again I display my lack of talent!!!). So, maybe our illustrious B17Engineer can come up with something???