(e) permanently imprinted or impressed thereon, and clearly visible from a distance of 20 feet a number corresponding to a permanent number on the gaming table to which it is attached and a marking to indicate game and shift, except that emergency drop boxes may be maintained without such number or marking, providing the word “emergency” is permanently imprinted or impressed thereon and, when put into use, are temporarily marked with the number of the gaming table and identification of the game and shift, and provided further, that the gaming operator obtains the expressed written approval of a Board Inspector before placing an emergency drop box into use.