Sergeant Platner was a scout for the US Army at the Mariposa Military Base in 2077.
Platner was a part of the security team at the Mariposa Military Base under the command of Colonel Spindel. He volunteered to go outside after the bombs fell to monitor the radiation levels. Led by Roger Maxson, he became one of the first Brotherhood of Steel members.
Not appearing personally, Sergeant Platner was mentioned in Captain Maxson's diary, which appeared in both Fallout and Fallout 3. Also mentioned in Fallout Bible.