Several years ago I noticed these old fallout shelter markers on the apartment block at 1901-1907 15th Street, N.W. There are at least four affixed to the exterior. These Cold War mementos are badly faded now; it’s hard to know whether a capacity was ever marked on the signs.
I always meant to do some research and write up the story of these yellow and black sentinels. But it turns out that Bill Geerhart did a much better job than I ever could have done. See also this photo gallery of signs still visible in Milwaukee and elsewhere.