CyberIsomorph

CyberIsomorph, or simply Isomorph, was the term an ArcHivist assigned to a variant of CyberNeomorph that was stranded, or isolated, in the late 20th century. (AUDIO: The Ultimate Cybermen)

Behind the scenes
"Isomorph" was coined by David Banks to distinguish the Cybermen seen in Silver Nemesis, who sported several cosmetic differences from the earlier "Neomorphs", as well as explaining why that story had them present in the 20th century, linking to the Neomorphs' earlier use of time travel in Attack of the Cybermen.