Typically the fraudsters will send out thousands of e-mails, but have also been known to approach the victim directly.
The conmen will then say that certain fees and expenses need to be paid, including government taxes, or death duties, to extract funds from the victim. Eventually the victim will be persuaded that the trunk contains a very large amount of cash which has all been stained black or another colour to avoid detection by customs.
The victim will then be asked to inspect the contents of the safety deposit trunk and told that the stain can be removed with chemicals. Some conmen even go as far as washing a stained note, replacing it with a real note when the victim is not looking.
Related to White Money.