1 coins dated 1961 had plain edges, but starting in 1964, the edges were lettered with the denomination and date. All 1926–1957 coins were then withdrawn from circulation and demonetized, with the majority melted down. Commemorative coins of the Soviet Union: in 1965, the first circulation commemorative ruble coin was released celebrating the 20th anniversary of the Soviet Union's victory over Nazi Germany, during this year the first uncirculated mint-coin sets were also released and restrictions on coin collecting were eased. In 1967, a commemorative series of 10 kop, 15 kop, 20 kop, 50 kop, and Rbl 1 coins was released, celebrating the 50th anniversary of the Russian Revolution and depicted Lenin and various socialist achievements. The smaller bronze denominations for that year remained unchanged. Many different circulation commemorative 1 Rbl. coins were also released, as well as a handful of Rbls 3 and Rbls 5 over the years. Commemorative coins from this period were always slightly larger than general issues, 50 kop and Rbl 1 coins in particular were larger, while the 1967 series of the small denominations were the same circumference but thicker than general issues. Initially, commemorative rubles were struck in the same alloy as other circulating coins until 1975, when its composition was changed to higher-quality copper-nickel with zinc excluded. Its specifications (31 mm diameter, 12.8 grams) were nearly identical to those of the 5-Swiss franc coin (31.45 mm, 13.2 g, cupronickel) worth approx. €4.39 or US$5.09 as of August 2018, resulting in the large scale use of (now worthless) Soviet commemorative coins to defraud automated vending machines in Switzerland years after they have been demonetized. Starting in 1991 with the final year of the 1961 coin series, both kopeck and ruble coins began depicting the mint marks (М) for Moscow, and (Л) for Leningrad. Banknotes Banknotes were issued by the USSR State Treasury (Государственный казначейский билет, Gosudarstvenny kaznacheyskiy bilet) in denominations of Rbl 1, Rbls 3 and Rbls 5, and by the USSR State Bank (билет Государственного банка, Bilet gosudarstvennogo banka) in denominations of Rbls 10, Rbls 25, Rbls 50 and Rbls 100. Colors are similar to the previous series but notes were much smaller in size. Seventh Soviet ruble, 1991–1993 The Monetary Reform of 1991 was carried out by Mikhail Gorbachev and was known also as the Pavlov Reform. It was the last of such in the Soviet Union and began on January 22,