Build 1098 was the first build that appeared, and lost this status in February 2011, when the build 749 was released. It was created at February 3rd, 2002. At this stage, it's largely different from the current S.T.A.L.K.E.R games as it is rather a Sci-Fi game called Oblivion Lost, which was like Quake or Unreal Tournament.
Since 1098 was the first build, it was a small tech demo and didn't have much at all. It has 1 level, 4 weapons (Only 2 weapons actually work), 1 kind of NPC, and a Female player.
A rather big level. It has a wide open grass field with mountains and trees, random abandoned tanks covered with the word 'Xray' (a reference to the Xray Engine), a big temple/pyramid, and underground rooms and tunnels.
Small robots with built-in machine guns. Comes in friendly and hostile types.