Speaking to the Arnold Schwarzenegger fan site the Arnold Fans, creator, co-writer (with William Wisher Jr.), and director of the first two Terminator movies James Cameron dropped a few hints as to how the action movie legend, who recently turned 70, may feature in the forthcoming trilogy of Terminator movies that are reportedly in development.
"Yeah, you got to ask yourself, 'Why did they make these characters look and sound like Arnold? There has to be a reason. So yeah, it has flashed through my mind that there has to have been a prototype. There has to have been a guy who's DNA was harvested from - that they grew the organic outer layer that they grew the Terminator from...and that presumably was a real person at some point. Now, the question is, did that person have some sort of meaning to Skynet on WHY they chose that one (Arnold)? Or was it like a whole rack of Terminators and the one that happened to be the Arnold model just happened to be closest to the door going out to the time displacement center and all the others looked different? I've asked myself these questions but it's never been resolved...so stay tuned! We're talking pretty seriously now about doing some new Terminator films or possibly a trilogy and you'll just have to see what surfaces in those."
What Cameron is referring to here is the model number of the Terminators. Each type of Terminator has a Series, Model, and Version number...
In the Terminator movie's Arnold always portrayed a Series 800 Terminator or T-800 (or a T-850 in Terminator 3: Rise of the Machines), whereas Robert Patrick portrayed a series 1000 or T-1000 in Terminator 2: Judgment Day. In the first movie, The Terminator, Arnold played a version 1 T-800, whereas in the second movie he played a version 2.4 T-800. The Model number for the T-800/T-850 that Arnold has portrayed to date is designated as the CSM-101 or Cyberdyne Systems Model 101. Put simply the Model 101 looks like Arnold, whereas the 102 would look like someone else, and the 103 looking like another someone else.
In short, the series denotes the chassis used, the model is the identity of the tissue sheath used, and the version is the age appearance of the tissue sheath used.
The belief or inference was that in addition to a bank of DNA materials from key donors, the Terminator's would snatch a resistance fighter and create a Terminator duplicate of them in the hope of finding the hidden Human Resistance bases - we saw this in one of Kyle Reese's dreams in the first movie where Franco Columbo portrayed one such Terminator (likely a T-800, but its model number is unknown - pictured above).
As in regards to the source of the DNA that was used for the CSM-101, this was semi-answered in a deleted scene from Terminator 3 with Arnold portraying Sergeant William Candy.
Cameron giving his own interpretation on this deleted scene should work just so long as he doesn't ignore the undeniable fact that while aesthetically poor, the events depicted in Terminator 3 (the inevitability of Judgment Day by 2004) are what would have followed the second movie. If Cameron ignores Terminator 3, out of pride or simple ignorance, he will damage the integrity of the entire series (that is by ignoring Terminator: Genisys ever existed, of course).