2006 New York Code - Stair And Elevator Identification Signs.

 
    §  27-393 Stair and elevator identification signs. Each stair and each
  bank of elevators shall be identified by an alphabetic  letter.  A  sign
  indicating  the  letter of identification for the elevator bank shall be
  posted and maintained at each elevator landing directly above or as part
  of the sign specified in section  27-391  of  this  article.  The  stair
  identification sign shall be posted and maintained on the occupancy side
  of the stair door. The letter on the sign shall be at least three inches
  high,  of  bold  type and of contrasting color from the background. Such
  signs shall be securely attached.