The war ended before the type's first flight and only a single prototype was built.

The aircraft wasn't bought, and only the single prototype was built.

A single prototype was built and tested, but it never entered production.

Only a single prototype was built, first flying on 22 April 1971.

However, In the notion of game above, is there a single prototype or several?

The single prototype was still being built when the war ended.

A single prototype was built in 1938 for evaluation purposes.

A single prototype was built, which remains operational as of 2012.

This only appeared in a single prototype and was not put into production.

A single prototype flew on 9 May 1918, but it was not put into production.