In 1985, the 100th anniversary of the birth of Niels Bohr, UNESCO minted a gold medal to commemorate the father of quantum physics and one of the most eminent scientists of the 20th century. Sculpted by Siv Holme-Muse of Sweden, the medal bears the profile of Bohr while the rear depicts his drawing of electrons orbiting around an atomic structure, his formula E2-E1=hy2 representing electrons in relation to hydrogen, and his signature. It also bears the inscription: Contraria sunt complementa (Opposites are complementary), Bohr's principle of complementarity.