from which the coins were struck took one impression from a 1942-dated hub and one from a 1941-dated hub (until the 1990s, dies required two strikes from a hub for the design to be fully impressed). Sinnock stated that the pieces were most likely struck in late 1941, when preparation of the 1942 dies was under way. Also produced at that time, though less apparent to the naked eye, was the 1942/1-D. Another popular variety is the 1945-S "Micro S", with a smaller-than-normal mintmark. This variety was caused by the Mint's wartime use of a puncheon (used to impress mintmarks on dies and hubs) which had been made for use with early 20th century Philippine coinage struck at San Francisco, which had only a small space for the mintmark. Beginning in 1928, coin albums were issued by private publishers, mostly in folder form, which were widely used to collect the pieces. This led to a great increase in interest in collecting current coinage by date and mintmark. Many Mercury dimes were not fully struck, meaning that design detail was lost even before the coins entered circulation. Exceptionally well-struck dimes display "full bands", that is, the horizontal bands on the fasces show full detail. In circulation, the reverse tended to more readily display wear due to a lower rim in relation to the relief of the design. Most well-circulated dimes show more wear to the reverse. Although no 1923 or 1930 dimes were struck at Denver, specimens appearing to be 1923-D or 1930-D dimes may be encountered. These counterfeits are struck in good silver, allowing the coiner to profit on the difference between the cost of production and the face value. They did not appear until after World War II, are invariably found in worn condition, and are believed to have been struck in the Soviet Union, a country known to have counterfeited US coins during World War II. Project Mercury Several Mercury dimes were flown into space on July 21, 1961, on the Mercury-Redstone 4 sub-orbital mission, the second manned flight of Project Mercury and the second human space flight by the United States. The coins sank with the capsule in the Atlantic Ocean, but were later recovered with the capsule from a depth of nearly in 1999. 2016 centennial gold version The Mint released a centennial version, in gold, of the Mercury dime on April 21, 2016, sold through