There are many highly valuable coins from the 20th Century. However, the most valuable is likely the 1913 liberty head 'v' nickel. One brought nearly 1.5 million dollars at auction.
Judy garlands shoe in may 2000 for $666,666
There are multiple military coins available. For custom collectors some of the most expensive coins can cost hundreds.
There were many more than 3 denominations. The most common ones in the 20th century were $2.50, $5, $10, and $20. In the 19th century there were gold coins with denominations of $1, $3, and $4 as well.
Most of the 20th century.
20th century by far.
The 20th. Century
The widespread minting of silver coins began to decline in the 20th century, particularly after the United States discontinued the use of silver in its coins in 1965. Other countries followed suit, largely due to rising silver prices and the costs associated with using precious metals in currency. By the late 20th century, most nations had transitioned to using base metals for their coins. Today, silver coins are primarily produced for collectors and investors rather than for everyday currency.
Most would consider the greatest inventions of the 20th century to be the automobile, the personal computer, and plastic.
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the 20th century
The 20th century
Back in the old days, most coins were made from either gold, silver or copper. During the 20th century, governments moved away from precious metals to mint coins due to the expense, and most coins were made from various combinations of copper, nickel, tin, aluminium, zinc and others. In the 21st century, a cheaper alternative became plated steel (iron).