13 stars above the eagle
13 steps on the Pyramid
13 letters in ANNUIT COEPTIS
13 letters in E PLURIBUS UNUM
13 vertical bars on the shield
13 horizontal stripes at the top of the shield
13 leaves on the olive branch
13 berries on the olive branch
13 arrows
13 colonies of course
Bound to be 3 more hidden

Happy 13th!