Learning to spot the most valuable 10-dollar bills means knowing what makes them worth so much. We're talking super old currency, special serial numbers, interesting mistakes in printing ...

Piano, 82, said many of the 100 dollar-bills were filthy and others ... The five or 10% that Banco Piano charges to exchange such currency for new notes accounts for about 1/10th of its business ...

“In fact, Paraguayan banks will not make a fuss over deteriorated guaraní bills but they would with a [deteriorated] dollar.” The guaraní is the oldest and most stable currency in the region ...