By Matthew Wells
BBC News, New York
This sculpture of Hercules is real, and dates from 300-500 AD
An exhibition which has opened in New York takes the unlikely step of placing fake works of art on display.
The Brooklyn Museum, like many others, began buying ancient Coptic and Pagan sculptures after World War II.
However, the museum's curators recently discovered that roughly a third of their collection is fake.
The resulting exhibition places genuine sculptures from the 4th Century AD alongside a small group of forgeries, probably from the mid-20th Century.
Experts say there is no way of knowing exactly who carved the limestone fakes, though one theory suggests they may have been produced by prisoners-of-war in Egypt.
Coptic and Pagan sculpture flooded the Western art market after World War II.
Edna Russmann, curator in charge of the exhibition - entitled Unearthing The Truth - hopes it will prompt galleries to examine their own collections more thoroughly.
"I know that other museums have fakes, (in) all kinds of fields and all kinds of subjects," she said.
Some of the fakes are easy to spot, but others display a high level of craftsmanship. Set among them are genuine works that have been touched up or re-carved.
The forgeries place a greater emphasis on Christian iconography than many of the real works - a sign, say experts, of them being made to order for European and North American buyers.
The exhibition continues at the Brooklyn Museum until early May.