From the National Archaeological Museum in Athens exhibition description:
Relief plaque. Parian marble. Found in Athens, near Theseion .
It most probably belonged to the facing of a funerary monument.
It represents a naked youth with a helmet running to right.
He may be an athlete participating in the hoplite race or
a pyrrhic dancer. The work is remarkable for the bold rendering of motion and for the figure’s coordination with the shape of the plaque.
About 500 B.C.