When Henry Voight designed the United States’ first copper coin in 1793, critics slammed the design.

“The American cents…do not answer our expectations,” wrote one journalist. “The chain on the reverse is a bad omen for liberty, and Liberty herself appears to be in a fright.”

The public joined in the penny pile-on. One critique: Lady Liberty’s casual locks signified madness or savagery. Another: the penny’s chain motif—intended to represent the interconnectedness of the founding colonies—reminded many Americans of the bonds of slavery.

The “chain cent” may have been unpopular in its own day, but last week, a single specimen sold for $2.3 million at a Florida auction, the latest in a series of high-profile coin sales that reflect all-time highs for the market. Coin World estimates that the 2014 market for coin sales was worth around $5 billion and listed 12 sales of more than $1 million. That included the $4.5 million purchase of a 1787 Brasher Doubloon and a Liberty Head nickel from 1913 that went for nearly $3.3 million.

These sales represent a new trend in the coin-collecting world. “15 years ago, a million-dollar coin was basically unheard of,” says Vicken Yegparian, who specializes in colonial and Confederate coins for Stack’s Bowers Galleries, told CNN Money. “Now a million-dollar coin is not commonplace, but not as big a deal as it was.”

Yegparian says that new collectors are one force driving the price of old coins to new highs—there's growing interest in coin collecting in emerging markets. And there are few big sales coming later this year: Sotheby’s and Stack’s Bowers will be selling off a stack of numismatic rarities, including “The King of American Coins,” an 1804 silver dollar so prized that the last specimen for sale garnered over $3.8 million.