17th and 18th century colonial governors usually required privateers to fly a specific version of the British flag also distinguishing them from naval vessels .
A specific version of the British flag is the 1606 Union Jack with a white crest in the middle .
17th and 18th century colonial governors usually required privateers to fly a specific version of the British flag , the 1606 Union Jack with a white crest in the middle , also distinguishing them from naval vessels .