The sentry bot is a pre-War model, as they can be found in locations that had been isolated from the Wasteland, for example inside the bunker in the lower levels of the toxic caves in Fallout 2. Many can also be found in the Sierra Army Depot. Compared to the sentry bot found in the Toxic Caves, they are much deadlier adversaries. Capable of packing as much fire power as a super mutant with a rocket launcher and minigun and extremely well armored. The Enclave are known to use them, as many of the bots can be found in the Enclave Oil Rig. It is the successor to the Mark I, and was only made in limited amounts.
Sentry bots are bipedal mechanical war machines, designed for only one purpose: war. They are heavily armored, and dispatch their foes with ease using their integrated minigun and rocket launcher. Being robots, though, they have a weakness in form of electro-magnetic pulses, which fry their electronics.
These robots are indeed a match for most player characters, and are almost exclusively found in the ending stages of the game. Armed with their heavy weapons they pose a major threat to any player not heavily armored enough, and their thick metal carapace is robust enough to withstand all but the most powerful weapons.
Sentry bots are fearsome enemies for all player characters. They wreak havoc using their integrated minigun and rocket launcher, and can withstand even the most powerful of attacks thanks to their heavily armored structure.