Now someone who knows Aerofiles better than I must help. What would be the attributes of an American aircraft whose description, written in many ways, would mostly return the same designs (as in my earlier guesses and the same of AviationBanter), which would be an one-off but manufactured by (in?) a company (not a home-built) but is not mentioned in Aerofiles at all. A concept aircraft, not considered a "prototype"? A concept aircraft of a designer who worked for a company and did something else for his main job? I tried to look names who worked with the "usual suspect" (see above) companies, the last was Otto C. Koppen, but to no avail.
