Look you moron, if the 1000 series is T-1000? Then guess what's the 800 series is? MORON! IDIOT! And as stated here, in one of the discussion in this page:
I agree with Christopher Thomas, below, regarding unclarified sources for this article.  Specifically, I take issue with the entire "Differences between the 800 and 850 series" section, because I contend that there is no such thing as a "T-850".  Stan Winston Studios, which designed the terminators for the films, confirmed this to me via e-mail when I wrote to them asking their opinion.  Their response (direct quote): "I'm not sure where the T-850 came from.  As far as I know, Arnold's Terminator has and always will be the T-800, model 101.  Now, the robot Terminators in T3 are T1's and Kristana Loken is the TX.  I hope that clears it up..."  While the term "T-850" is somewhat widespread on the internet, even extending to T3-related merchandise such as action figures, its origin is, to my mind, something of a mystery.  Rich 
 Stan Winston DESIGNED the Terminator, and he says it's T-800! Now shut the fuck up and change it back you idiot!