So a week ago on reddit, this guy posts saying he has this disc that was given to gaming journalists back in 1997 as an early demo of the game http://imgur.com/a/0QsPP. A valve employee asked him about his reddit post, and the guy with the disc asked the valve dude to go check with the rest of the valve guys to see if it'd be ok if he posted it. Apparently he didn't hear back after a week so he's now posted it all anyways.
The maps included with it:
Only three weapons appear to be in the game, pistol, crowbar, and mp5 with working grenade launcher. Unlimited ammo and no reloading for both guns. The crowbar fucking sucks.
Also of interest are demo files for most of the maps, where you can watch some guy from 1998 playing through the maps (badly and usually with god mode). type 'playdemo *map name*" to view them. Not all maps have them.
As far as cut content goes, you can see non-functioning panther-eye monsters, working minigun troopers and lots of old models for basically everything but alien/human grunts and vortigaunts. And also pressing 5-9 number keys playings saxophone sounds and jazz music and other random shit because why not.
HOW TO RUN:
Also for any video drive errors you get, like it says above:
MODEL VIEWER AND COMPILER:
USEFUL COMMANDS AND STUFF:
And some facts about the demo
The hi-poly robot seen in the starting map was made as an engine stress test deal, to try and crash the engine (but it failed to crash it). It's a robot from some anime series called robotech. Don't forget to shoot it for a little surprise
And last but not least, the guys now trying to sell the disc on ebay lol. The contents of the disc are still all online, though.