I guessed (incorrectly) that the answer was a "metal enclosed isolation switch," and my rationale was mostly centered around the isolation aspect. Does anyone know of any sources I can read that can help clarify this? I'm guessing the correct answer was "bolted pressure switch" but I'm not sure why that's any more correct than the answer I gave, although I figure it's got something to do with the high current associated with the incoming service.
Thanks!