Signs of the Times

"Hobo Symbols of the Great Depression" = Adventurer Symbols of the Megadungeon?

Could be used by the PCs, Thieves Guild, or a secret cult, or found by them while duneoneering, used as hints, misdirection, red herring... 
Several would require a broad interpretation, or even an alternate meaning to incorporate into a fantasy setting.  Could also be adapted as a Random Encounter or Random Dungeon/Town  Design table, or your next Dungeon/Map could be marked with symbols...
Several more charts of varying sizes can be found with an image search.
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