Second Blue Book unknown at Selfridge AFB air defense base, Michigan (1952)

Project Blue Book Case #1680. On July 27, 1952, an unidentified object was observed at Selfridge AFB — the second Blue Book unknown from this Air Defense Command installation (following Case #1380 from July 3). Two unknowns in 24 days at a base whose specific mission was identifying aerial threats was professionally humiliating. July 27 was during the peak wave week. The case was classified "Unknown."