There are four σ6 IQ societies at the present.
GIGA society by Paul Cooijmans
SIGMA SIX society by H.Melao Jr
NANO society (Nano condition of the Ultima society) by Ivan Ivec
ESOTERIQ society by Masaaki Yamauchi
The theoretical rarity of σ6 IQ score on normal distribution is well known to all people in high IQ community as one in one billion.
Because of the extremely rarity, σ6 IQ score has been kept the authority and Myth and often cause a misunderstanding since high IQ community was born.
Currently, there are many tests being possible to measure σ6 IQ score in high IQ community, but some of them has no reliable norm reports.
Additionally speaking, the ESOTERIQ society will keep eternally the authority as a σ6 IQ societies as well as the Giga society.