Its a 1966 Ford Mustang Convertible that Ford and the Management of the Empire State building decided to display on the observation deck as a PR stunt.
The car was cut into 4 main sections and modified with brackets so it could be transported in pieces up in the elevator and bolted back together on the observation deck to look like the standard car.
On October 20 1965 , they disassembled the car at the base of the Empire State Building and after putting the sections in the elevators took them up to the 86th floor observation deck and bolted the car back together.