This is strange. The Comet ad you posted looks 99% similar to the mystery car. Infact I think it is the same car. The car in the ad I have, however, has a different name and was produced in another state. It is by a company which is lesser known as the Comet but still sold cars for few years. The car encyclopedia I have doesn't connect the two companies together in any way
Maybe they simply stole the picture to their advertisement. It is also possible that the company bought kits from Comet and assembled the car in their own factory under a different name.
I think I should award you with a point because it is likely the same car...
The company I'm looking for was based in central US...