A first or preliminary model of something (a machine), from which other forms are developed or formed.
The difference between "Prototypes" and "Specials" is sometimes hard to determine. This is how I decide where a car belongs: Specials were built with the purpose to be sold to the public, Prototypes are built for development and/or research purposes. With these simple rules, some cars are still hard to catalog (as I will explain below), but I hope you will still find everything you need on this site.
Some exotic, one of a kind Corvettes are mistaken for prototypes, while they’re actually modified production cars. Special VIP customers or large dealers sometimes ordered an option on a car that was not available on the option list. These cars were called ”COPO” or Central Office Production Order. Such a car is marked as a Special, since it’s built for the market. Another example of such a special built car is the FSO, Factory Shop Order or Fleet & Special Order. This car was modified in the factory to celebrate a special occasion like a best selling dealer, a charity donation, etc.
A more covertly used code is ”SO”, or Shop Order/Special Order. These were special orders placed by the GM Engineering or GM Styling department. Think of standard Corvettes with exotic engine or drivetrain parts in it or special styling tests, like the four seated C2 you will find on this site.
GM built quite a lot of test vehicles. To try out new looks, a new technology or just to test the reaction of the public to a new style for the next generation Corvette. Cars falling under this category were not meant to be sold. Prototypes can be non-functional clay mock ups, like the early C4 design study shown below.
They can also be fully functional vehicles, like the 1954 Motorama showcar line-up shown below. Most often, after the prototypes served their purpose, the order was given to destroy it. This way, a lot of them are gone now. However, quite a few survived because the order was not followed through or the scrap yard secretly kept the car.