Archimedes Principle at Work

The picture shows an electronic balance that has been adapted to allow a coin to be weighed first in air and then in water. Archimedes principle readily permits the calculation of the density of the coin. If the density measured in this way is significantly different from the known density of the genuine coin, this gives an almost certain indication that the coin being examined is a counterfeit one.

Other methods of detecting counterfeit coins are described in the book “Germany’s Gold”. These include the use of eddy currents, magnetic testing and, in the case of counterfeits that use the correct alloy, careful visual examination.