The United States Post Office Branch in Middleborough, Massachusetts still sports both an exterior and at least one interior sign.
Inside one interior sign is over the stairs to the basement area
This post office is by no means unique in having been designated as a Fallout Shelter; multiple other branches throughout Massachusetts and the United States were also designated based on their size and construction alone. Many still only have exterior signs if they have them at all, so seeing an interior sign still intact is somewhat unique.
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