counterfeiter

Japan is set to introduce a new set of bank notes this summer, something it does every 20 years or so to thwart counterfeiters.

"These responses are impossible to duplicate, as long as the glue interface is destroyed by a counterfeiter," Han says.

"We recognize the limitations of this exercise and are conducting physical investigations where warranted," Novo said, adding this at times involved specialised firms "on the ground" to help authorities track down counterfeiters.

Life complicates when the agents go undercover to trap Masters and must break the law to get close to the counterfeiter, with potential deadly consequences.

And counterfeiters often found the bills easy to copy, devaluing the real stuff with a flood of fakes.