You didn’t indicate if you emailed KC so I did. In the meantime, here’s the logic I used.
The aircraft does have a basis for its type:
The type certification basis for the Dornier Seastar Model CD2 airplane is as follows: Part 21 of the Federal Aviation Regulations (FAR), § 21.29; Part 23 of the FAR, effective February 1, 1965, including amendments 23-1 through 23-34; Special Federal Aviation Regulation (SFAR) No. 27, effective
February 1, 1974, as amended by amendments 27-1 through 27-8; Part 36 of
the FAR, effective December 1, 1969, as amended by amendments 36-1
through amendment 36-18.
and was assigned a type certificate:
(Docket No. 061CE, Special Conditions 23-ACE-44)
Special Conditions; Dornier Seastar CD2 Series Airplanes and Exemptions for FAR Part 23 Amdt. 34 §23.807(d)(1) and §23.807(d)(1)(i)
based on the Luftfahrt Bundesamt certifying the aircraft
The Luftfahrt Bundesamt originally type certificated this aircraft under its type
certificate Number 2065. The FAA validated this product under U.S. Type
Certificate Number A62EU. Effective September 28, 2003, the European
Aviation Safety Agency (EASA) began oversight of this product on behalf of
Germany.
The FAA says the
Import Requirements. This aircraft is not eligible for operations in the United States. Please contact the FAA, Small Airplane Directorate at Kansas City, Missouri for additional information.
Because it says “import requirements,” I took this to mean that the aircraft, as being certified by a recognized foreign civil authority, would be allowed to fly in the USA but could not be put on the registry.
I’ll let you know if I get a reply back from KC