File talk:Anahit Stamp.jpg
http://en.wikipedia.org/wiki/Phrygian_cap
Phrygia is as far back in time as I go looking for the history of symbols in art. The next step is prehistory, Greek Vases, Mythology and Troy. So, the Phrygian Cap is the oldest symbol in written history. Which is not to write of older symbols in art without solid expert opinion.
