A one-of-a-kind California Gold Rush coin, preserved for years by one of Baltimore's most prominent families, will return here next month for the first time in nearly 30 years.

In March, Steve Contursi paid millions for one 1794 silver dollar and more for the collection it was in. But he thought the expensive and surprisingly shiny coin, 40 millimeters in diameter, might be something even better, something no one realized still existed.