The Shetland Flock Book Society was formed in (1927) by Shetland breeders in Shetland with the aim of preserving the classic Shetland, preventing loss of type through crossbreeding or indiscriminate breeding. They wrote the Shetland Breed Standard to describe the type of sheep that they wanted to preserve and promote.   The Shetland Sheep Society (dealing with the United Kingdom outside of Shetland) also uses this standard and NASSA's predecessor adopted a similar standard for use in North American in 1991. NASSA reaffirmed the 1927 Shetland Flock Book Society Standard  in 2000.