Type Zero (タイプゼロ Taipu Zero) refers to the prototype Combat Cyborgs who served as a template for development of Jail Scaglietti's Numbers.
History
Although the theoretical basis necessary for construction of Combat Cyborgs was developed by Scaglietti in 0050, 25 years before the JS Incident, practical results were first achieved by another scientist, whose identity is yet to be revealed. Scaglietti and his subordinates refer to the products of this expert's work, Subaru and Ginga Nakajima, as "Type Zero".
Some time before the Combat Cyborg Incident of 0067, Quint Nakajima led an investigation of a Combat Cyborg development facility and discovered the two girls. Learning that both contain her own (presumably stolen) genetic material, she adopted them as her own children. It has been speculated that Quint's genetic material was leaked through the same source of corruption within TSAB that later killed her and the rest of Zest Grangaitz's team.