I don't have the answer to this, and I never heard anyone explain why...but in the 1960's Bills logo, there is a player and a buffalo behind him (too lazy to look for it on google, but old-timers know what it looks like).
Anywho, the player wears number 31...and for the longest time, no player was issued number 31 until it went to J.D. Williams in the '90s (right?)...but I've never heard why the player in the logo wore number 31, and why that number was so special (sorta like the Rolling Rock "33" mystery).
Lori, Rockpile, anybody, HELP!!!