A novel embedded impedance measurement system for counterfeit detection of bimetallic coins is presented. The system integrates Eddy current sensors with inductive spectroscopy, facilitating the detection of hidden inlay security features and the identification of surface minting. A salient feature of the system is the use of a single Eddy current sensor that operates across multiple frequencies. This feature eliminates the need for extensive calibration procedures typically required when multiple sensor coils are used for each excitation signal frequency. The system employs an undersampling...