The Tribune de Genève newspaper reported on Wednesday that fake coins have been circulating around Geneva and Lausanne for two months.
First to react to the problem, Swiss Post, the national post office, has trained its staff to recognize the imitation coins, which are the same weight as real five-franc pieces, but are less shiny and are more coarsely engraved.
Swiss Post employees have identified fake coins in “numerous cases”, the paper reported.
Any detected coins are then taken out of circulation and sent to the federal office of counterfeit currency.
A spokesperson for the Swiss federal police told the Tribune de Genève that it is conducting an investigation but that it cannot, at present, determine the extent of the fraud.
National coin-maker Swissmint is currently conducting an analysis of the counterfeit coins.
As yet, no public safeguards have been put in place.
Last year, 787 fake five-franc coins were seized in Switzerland.