This constraint is one reason researchers have focused on the question of whether Cooper could have spent the money without detection. The answer is: possibly yes, in the right circumstances. In the early 1970s, the serial number list was circulated but not searchable in real time. By the time electronic systems that could rapidly check serial numbers became widespread, more than two decades had passed, and the bills would have been significantly deteriorated regardless.
The near-total absence of the money from any reported detection may also reflect the simpler possibility that Cooper died in the jump and the money was never spent because there was no one to spend it. The 1971 currency would be rare collectors’ items now regardless of how it was acquired; any Cooper ransom bill that appeared at auction would be immediately identifiable and would draw enormous attention.
Brian Ingram’s 2008 auction demonstrated this: his 15 bills, with face value of $300, sold for more than $37,000. The ransom bills have acquired a value in the collector market that far exceeds their face value—a value derived entirely from their provenance in one of the most famous unsolved crimes in American history.
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## What Has Changed Since 2016
The FBI’s 2016 suspension of active investigation did not end the public’s interest in the case, and it did not stop researchers and investigators outside the bureau from continuing their work.
Several developments since 2016 have received coverage, though none has been confirmed by the FBI as constituting meaningful new evidence.