The prototype, Nasty, was designed and built in 1957 as a private venture by Westermoen of Mandal, Norway.

Following this Westermoen received orders from the Royal Norwegian Navy (for whom they were known as the Tjeld class), and from the navies of the United States, (who called them the Nasty class), Greece and West Germany.

Six vessels were also built in the United States under licence (some parts, such as the keel and stem being imported).

The prototype, the patrol boat Nasty, was designed as a private venture in 1957 by A/S Båtservice of Oslo, in close cooperation with Royal Norwegian Navy officers with World War II experience in fast patrol boats: The chief designer was naval architect Jan Herman Linge.

[1] The United States Nasty class of fast patrol boats were a set of 22 vessels built for the United States Navy (USN) to the Norwegian design and purchased in the 1960s for "unorthodox operations" during the Vietnam War.