The letters of the alphabet exhibit five varieties of symmetry (or non-symmetry):
A M T U V W Y have left-right (vertical) symmetry (.272) v
B C D E K have up-down (horizontal) symmetry (.218) h
N S Z have 180 degree (rotational) symmetry (.137) r
H I O X have all three symmetries (.205) a
F G J L P Q R have no symmetry (.168) n
Eckler, A. Ross
"Symmetries of the Alphabet,"
Word Ways: Vol. 40
, Article 3.
Available at: http://digitalcommons.butler.edu/wordways/vol40/iss3/3