In God We Trust. In machines? Not so much.

An unknown number of new U.S. $1 coins bearing(1) the image of George Washington are missing the words "In God We Trust" and other lettering along the edges, the U.S. Mint said on Wednesday.

The Mint released more than 300 million gold-coloured, George Washington $1 coins last month, but it recently discovered a problem. The coins, made by the Philadelphia Mint, were supposed to have the inscriptions(2) "In God We Trust," "E Pluribus Unum," the date and the mint mark around the edge.

It is unclear how the mistake occurred or how many of the coins are in circulation, according to the Mint statement. The Mint said it would make necessary technical adjustments in the manufacturing to eliminate the defect.

"The United States Mint understands the importance of the inscriptions 'In God We Trust' and 'E Pluribus Unum' as well as the mint mark and year on U.S. coinage(3). We take this matter seriously," the statement said.

"We also consider quality control a high priority. We are looking into the matter to determine a possible cause in the manufacturing process."

Robert Hoge, curator(4) of North American coins and currency for the American Numismatic (5)Society, said that collectors find coins with a mistake like this, known as a Mint error, desirable when a relatively small number are in circulation.

"Since it was an accident, there is no count of how many were created. That's always the question with a mint error and it's difficult to tell how many there might be," he said.

On the auction Web site eBay, one of the coins sold for $405 .

One of the most famous Mint errors in the United States occurred in 1922. That year, "through carelessness or overzealousness(6)," Hoge said, a defective dye(7) for the obverse(8), or head, side of the 1-cent piece failed to show the "D" mark indicating it was struck at the Denver Mint. One of those coins in mint condition would fetch upwards of $10,000, Hoge said.

1. bear：印有

2. inscription：题字

3. coinage：造币

4. curator：馆长、负责人