Does anybody know what it was (I'm asking strictly about planes that saw combat, not the "blueprint superfighters")?

It never saw combat, but it had been flight-tested and was on the
"production line" at the Gotha works: the Horten all-wing
fighter-bomber.

all the best -- Dan Ford
email:

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com