This toggle has a small radio emitter and a tiny power cell. It likely links to a control computer, like an on/off switch. This toggle can be used to toggle on/off the force fields on levels 1-3 of Mariposa Military Base.
While not featured in the final version of either game, it can be found in the game files of both Fallout and Fallout 2.
Behind the scenes
“I am pretty sure that both of these items were part of deleted quests. Tangler's Hand was used to prove that you killed someone (duh, Tangler probably), and I think it was in Adytum, which was heavily modified near the end of FO's development. I am even less clear on the field switch, but I remember we had lots of discussion on how to handle the player bringing down the force fields in the Military Base, so it was probably going to be used for that, but then got tossed aside when another solution was used.