The jewel box had been in a Plexi-glas case equipped with an alarm that sounded after it was stolen, she said, adding that police arrived in less than five minutes.
Both thefts were caught on security cameras, she added.
After the first theft in November, Fogarty said the museum added extra security guards and cameras.
"Obviously, we'd like our security measures to be better or this wouldn't have happened," Fogarty said. "But we do feel confident with that steps we took were appropriate and the enhanced security measures will aid in this investigation."
Thanawala reported from San Francisco.
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