MIAMI - Thieves stole a $550,000 gold bar from a treasure museum where it went on display after a Florida salvager recovered it from the wreck of a Spanish galleon that lay on the ocean floor for centuries, the museum's executive director said.

The 74.85-ounce gold bar was stolen on Wednesday from the Mel Fisher Maritime Museum in Key West, Florida, in what executive director Melissa Kendrick called "a very quiet smash and grab".

The 28-cm gold bar was inside a glass case with a small opening where visitors could stick a hand inside and lift the bar to examine it.