The Cyberdyne Systems Model 101 living tissue skin was based upon Sector Agent Dieter von Rossbach from government files that pre-date 2001. As a government agent, numerous databases later possessed by Skynet were available to provide ample representation of many physical appearances. When it came to creating the human tissue model for T-800 Terminators, Skynet used this stored information, along with the data from various other resources, to model the Infiltrator faces on as the closest physical match to contain the Terminator endoskeleton. The Model 101 has been used at least on the T-800 as well as the numerous "contemporary" Terminators created in the present by Serena Burns in her Secret Terminator Lab.
Terminator 3: Rise of the Machines
The Cyber Research Systems Model 101 living tissue skin was based upon U.S. Air Force Chief Master Sergeant William Candy from 2004. Volunteering to give his likeness to future military robotics, Sergeant Candy's head was laser scanned by Cyber Research Systems, the resultant three-dimensional representation of his face being stored for future use. When it came to creating the human tissue model for T-800 Terminators, Skynet used this stored information, along with the data from various other human head scans, to model the Infiltrator faces on.
In a deleted scene (later restored into the Special Edition) from Terminator 2: Judgment Day, it is shown Cyberdyne Systems Series 800 Model 101 Version 2.4 inside the Terminator's HUD while he reboots.
↑Shown on screen in the special features from the Terminator 3: Rise of the Machines DVD, which identifies the T-850 as an "Series 850 Model 101", and the older Terminator as an "Series 800 Model 101". (Note that the T3 DVD Extras swap the order of Series & Model for all references, not just the new ones.)