Online Encyclopedia of Western Signs and Ideograms Symbols.com

Symbol 4:23

0420b

04:23 · This sign from the ground-to-air emergency code means I/we proceed in this direction according to some sources.
    It is also a main part of the sign 0660, reported to have been seen in 1964 by a man from Socorro, New Mexico, as a sort of logotype on an elliptical, unidentified flying object, i.e. a UFO.