More than 300 bogus coins with dates between 1873 and 1878 were seized at O'Hare International Airport last week, officials said.
The coins were made to look like popular 19th century coins worth more than $2,000 each.
Border and customs officials in Chicago intercepted the shipment of 361 counterfeit coins from China as the coins made their way to an Illinois man who intended to sell them online.
"Legitimate traders are being duped into buying these coins believing they are genuine," said David Murphy, the CBP's director of field operations in Chicago. "We strongly recommend buyers or any consumers to be aware and use caution when making these types of purchases on the internet."
Officers became suspicious of the shipment when they noticed an anomaly on the X-ray of the package.
The original U.S. Trade Dollar coin was minted from 1873 to 1878. Research revealed that some of these coins can be sold for as much as $2,000 each, the release said.
A sample coin was turned over to a U.S. Customs and Border Protection lab in Chicago for analysis and showed the coins were made of brass with a thin silver plated coating, officials said.