You've stumbled upon a story that's fun and fascinating at the same time. You're about to enter the world of the Great 1964 Coin Shortage.

In the late 1950s and early 1960s, the United States faced a problem born of success. The economy was growing, new technologies were being introduced, and the population was surging. The nation's monetary system had failed to keep up. Largely unchanged since 1792, coins in America were still minted in limited quantities from precious metals.

In the 1950s, a booming American economy became fascinated with automatic vending machines. From its introduction in the late 19th century and its pinnacle as the Automat, coin-operated machines became ubiquitous in the 1950s. There were parking meters, telephones, juke boxes, pinball machines, automatic toll-collectors, coin-operated laundromats, and vending machines for cigarettes, food, soda and even ordinary soft goods. These gobbled coins voraciously, and the nickel ─ prices being what they were in the 1950s ─ was the coin of choice.

All those machines had to be stocked with goods, and American industry met the need, as American manufacturing surged in the 1950s and 1960s. American factories were producing more than twice as many goods in 1965 as they were in 1950, and the pace of increase would accelerate through the 1960s. This led to increased demand for raw materials, and precious metals were not immune. Thanks to surging demand, the price of silver shot up by almost 40 cents per ounce between 1960 and 1963, leading to an arbitrage business whereby companies would buy old coins simply for their silver content, then melt them down and sell the resulting bullion.

Until 1964, the U.S. Mint had made use of America's vast silver reserves (which were used, incidentally, to great advantage during WWII by the Manhattan Project). By the 1960s, even those vast stocks were running low. In 1964, the U.S. government announced that America's 1 billion-ounce silver reserve would be exhausted by 1966 unless the coinage of the United States was changed. This was a huge deal; the formulation of American coins hadn't changed very much since 1792, but in 1965, President Johnson asked Congress to reformulate American currency to eliminate silver from quarters, half-dollars and dimes. Here's his message to Congress.

As the New York Times reported, "the solution came not a moment too soon," but this is only part of an answer to your question. After all, nickels don't use silver, and they didn't even in 1965. Why, then, was there such a huge production?

Two reasons. The first is that nickels benefited from the surge in production before other coins because their raw materials weren't in shortage. In the early 1960s, the U.S. Mint began expanding its facilities hugely, making up for years of neglect in the 1940s and 1950s, and started running its plants overtime. Silver-based coins were limited in supply because of the raw material shortage I mentioned before. Hoarders would collect the silver-based coins because they feared a shortage and ironically contributed to that shortage, per Gresham's Law. Nickels didn't face that problem, but they benefited from the increased production. No one wanted nickels, but they were being produced at a fast pace just as the silver-based coins were. Nickels were among the first to benefit from the Mint's new techniques. Instead of producing nickel strip by itself, it began purchasing it from private contractors. Bronze strip for pennies came next.

The second reason is that in addition to the surge in production, Congress approved legislation that allowed the Mint to produce 1964-dated coins as late as July 1, 1965, a measure intended to dodge hoarders. While this was targeted at the silver-based coins, it also affected the nickels. Because no one wanted to hoard nickels, they stayed in circulation even as hoarders scooped up the silver-backed dimes, quarters, half-dollars and dollars.

So when you see an abundance of 1964 nickels, know that you're observing a vestige of a unique American crisis, one resolved through a change that uprooted almost 180 years of history.