Let's go back in time. Way back. Keep going. OK, stop. You're in the Ptolemaic Period. It's somewhere around 304 to 30 B.C. You're in Egypt. You're playing Dungeons & Dragons. Except back then, it's more like Pyramids & Petsuchos.
The Metropolitan Museum of Art owns what may be the world's oldest d20 die. It's made out of serpentine and looks to be in remarkably good shape for its age.
The die is a little over an inch tall. The symbols carved into the die appear to be of Greek origin, in keeping with it coming from the Ptolemaic Period.