July 1992 by setting up restrictions to the flow of credit between Russia and other states. The final collapse of the rouble zone began when Russia pulled out with the exchange of banknotes by the Central Bank of Russia on Russian territory at the end of July 1993. The Kyrgyz som was introduced on May 10, 1993, replacing the Soviet currency at a rate of 1 som = Rbls 200. Initially only banknotes were issued, coins were not introduced until 2008. Coins Circulation coins were first introduced in January 2008, making Kyrgyzstan second to last of the former Soviet republics to issue them. Belarus became the last. This move came with growing demand from vendors for coins, especially from slot machine industries and those desiring a more efficient system for collecting fare money. The coins were issued in denominations of 10 and 50 tiyin and 1, 3, and 5 som. A 10 som coin was issued a year later in 2009. All coins are minted by the Kazakhstan mint in Ust-Kamenogorsk and bear some resemblance to coins of the Russian Federation. Commemorative coins There are several commemorative non circulation coins struck in silver and gold, and a special collector's 1 tyiyn piece struck in brass. Starting in 1995, the National Bank of the Kyrgyz Republic has issued a large number of commemorative coins intended for collectors. They are not used in everyday circulation. Banknotes On 10 May 1993, the government issued 1, 10, and 50 tyiyn notes and the Kyrgyzstan Bank issued notes for 1, 5, and 20 som. In 1994, the Kyrgyz Bank issued a second series of notes in denominations of 1, 5, 10, 20, 50, and 100 som. A third series followed from 1997 onwards in denominations of 1, 5, 10, 20, 50, 100, 200, 500, and 1,000 som. A fourth series was issued in 2009 and 2010 in denominations of 20, 50, 100, 200, 500, 1,000, and 5,000 som. Several commemorative banknotes intended for collectors were also issued. First series (1993) Notes valued 1 and 10 tyiyin with serial numbers KT and ZT were issued in 1999. 50 tyiyins notes with serial numbers KT and ZT were issued in 2001. All others in 1993. Notes of the first series were designed by Dmitry Lysogorov and A. P. Tsygank. They were printed by De La Rue in Great Britain. Notes valued 1, 10, and 50 tyiyin stayed