5 Roubles Vostok Station; Hafnium

(en) Vostok Station (Russian: Станция Восток) is a Russian (formerly Soviet) research station located near the Southern Pole of Inaccessibility, at the center of the East Antarctic Ice Sheet. Vostok Station is located within the Australian Antarctic Territory (although as a signatory to the Antarctic Treaty System, Australia does not exercise sovereignty over the territory). Vostok research station was established on December 16, 1957 (during the International Geophysical Year) by the 2nd Soviet Antarctic Expedition and has operated year-round for more than 37 years. The station was temporarily closed in January 1994. This station is now cooperatively operated by Russian, U.S., and French scientists.
Apparently, Vostok is the coldest place on earth, reaching temperatures of -90°C. The station has a permanent number of scientists all year-round.
 
In 2008, Fred Zinkann has produced coin in various metals on Vostok Antarctica Station with face value of 5 Russian Rubles to commemorate 50th years of operation 1958 to 2008.