W: H:
mark top+bottom-only in green
mark middle only in yellow
top: mid: bottom:
Symbols that only occurs outside the middle area (0):

Symbols that only occurs inside the middle area (0):

Middle area (X symbols, X unique):

Outside area (X symbols, X unique):

This widget investigates the observation that an unusual number of symbols are missing from the middle rows, as noted by members of the zodiac killer site forums
github - font by Largo & zodiackillerciphers.com