According to this article at CNN.com a gold ingot that’s been on display as part of a huge coin collection in the museum’s National Numismatic Collection that was thought to have been from 1857 might actually only date back to the 1950s.
Not that it matters. Even if it is a fake it’s still valuable to the museum. Turns out that phony coins and ingots are quite common in all museum collections. While it’s status as possibly a forgery is an important determination that should be made it will still prove useful as an aid in detecting other fake coins and ingots made by the same person or people and this will remain as part of the collection.