> 10 years went by and the search for Mister 880 turned into the largest and most expensive counterfeit investigation in Secret Service history.

The article doesn't explain why the Secret Service made this their biggest case, and it doesn't make much sense to me. If the dollars were accepted by the general population, it would cause an infinitesimal increase in inflation of no consequence to others. And if shopkeepers wised up to the false dollars and rejected them, at worst he was defrauding the public by a few hundred dollars a year. In either eventuality, surely the Secret Service had more notorious counterfeiters to track down?