Sphinx ring sterling silver

Sphinx ring in recycled sterling silver.
 
"There are two sisters: one gives birth to the other and she, in turn, gives birth to the first. Who are the two sisters?"
 
Oedipus met the Sphinx who was feared for eating men who couldn't answer her riddles. Oedipus answered her riddle correctly, winning him the throne of Thebes and married the widowed queen, who was in actuality his own mother.
 
Ring size = inner diameter of the ring in mm.