1999 Russia 3 Roubles The First Tibet Expedition 1 Oz Silver Proof Coin. Series: Russian Explorers of Central Asia. Metal fineness: 900/1000 Silver. Fine metal content: 31.10 g. Diameter: 39.00 mm. Thickness: 3.30 mm. Mintage: 15,000 pcs. Edge: Reeded, 300 corrugations. Mint: (????) Saint Petersburg / Leningrad / Petrograd.