This is a beautiful sheet consisting of 6 stamps, issued by St. Thomas & Principe in 2008, featuring famous naturalists. Included on the sheet are French volcanologist & geologist Haroun Tazieff, English ornithologist John Gould, Canadian petrology & mineral crystallization expert Norman L. Bowen, German polymath Johann Wolfgang von Goethe featured here with orchids, Russian physiologist who also won the Nobel Peace Prize in Medicine Ivan Pavlov, and English geologist Charles Darwin. The sheet is Post Office fresh, mint never hinged.