The CRV-III was the third prototype build by Centaur, but was not a complete car. It was built for crash testing. Needless to say, plastic cars do not afford a great amount of protection. During the test, the car was demolished.
The next step was to build a more practical, street version of the car, so CRV-IV was build in February 1966. It featured a full windshield and Coupé roof. The doors opened in the conventional method, but the side windows were part of the roof and opened "gullwing" style. Again, the car was Corvair-powered.
A second Coupé, CRV-V, was built a short time later. Both cars were immediately sent overseas to promote the use of plastic at Marbon's foreign production facilities. It is not confirmed if either car was ever returned to the USA.