In my memory, the definitive version of the T800 is the horrifying de-skinned Endo-Skeleton revealed at the climax of The Terminator:
Arnold Schwarzenegger minus his skin; the seemingly unstoppable T800 Model 101
There have been numerous Terminator Endo Skulls available on the market over the years for a premium price, most recently from Sideshow Collectables. They tend to fall into two categories: clean (shiny chrome) and battle-damaged (weathered with a sooty/grimy finish):
Sideshow Collectables Clean and Battle-Damaged T800 Endo Skulls
Although great pieces in their own right, these display-worthy Endo Skulls have details/features that I believe can be improved upon, or are not an iteration of the T800 that is the 'true' version in my eyes (see above). These are namely the eyes, the teeth, and the neck rods/hoses. The Sideshow skulls (and to be honest most other versions of the skulls) seem to be referencing the T800 from Terminator 2 onwards, where as I will be looking at the original CSM101 endoskeleton as my point of reference.