About 20 years ago I saw a sign off Jefferson Blvd. near its intersection with Lincoln Blvd., in the Ballona Wetlands area of Los Angeles. The sign was at the edge of “Hughes Airport,” a landing strip Mr. Hughes had built in what was pretty much the middle of nowhere at the time.
Anyway, the sign I saw had no words, just several series of three lines, either verticle or horizontal. (Remember the “illiterate” eye chart from grade school?) No words, just sets of three lines, in dark brown or black, getting smaller as they progessed left to right and down the surface of the sign. Was this some kind of aviator’s code?