GIBRALTAR. Azure, between two pillars a castle argent, masoned sable, from the gate a golden key pendant, subinscribed " Plus ultra." [Refer to grant to Lord Heathfield, 1787, "the arms of Gibraltar" being granted to him as a chief of augmentation.] But the arms as published by the Admiralty for use upon the Union Flag by the Governor are "gules, a triple towered castle proper, and suspended by a chain from the gateway, a key or. Motto — " Montis insignia calpe."
Original Source bookofpublicarms00foxd_djvu.txt near line 10786.