Method for detection of metal bodies in test objects comprising the steps - exciting a magnetic alternating field, - individually moving exemplary test objects without metal body at a defined velocity through the magnetic alternating field, registering first variations of the magnetic alternating field by the exemplary test objects individually moved therethrough, - determining a variation limit for test objects without metal body of a predetermined shape, size and composition using the first variations, - individually moving test objects to be tested through the magnetic alternating field, - registering a second variation of the magnetic alternating field by the respective test object individually moved therethrough, - comparing the second variation to the variation limit, - if the second variation exceeds the variation limit, generating and outputting a metal warning signal, - wherein, in determining the variation limit, at least one third variation, which is one of the first variations or a generalized variation derived from the first variations, is superimposed at different temporal offsets with a first variation function, which corresponds to a fourth variation of the magnetic alternating field when moving the metal body of the predetermined shape, size and composition at the defined velocity through the magnetic alternating field, to provide virtual fifth variations, - wherein the variation limit is determined such that it is exceeded by all fifth variations but none of the first variations, characterized in - that, in determining the variation limit, the at least one third variation is superimposed at the different temporal offsets with a second variation function, which corresponds to a sixth variation of the magnetic alternating field when moving a metal body of the predetermined shape and composition but of a smaller size at the defined velocity through the magnetic alternating field, to provide virtual seventh variations, - wherein it is tested whether the variation limit can be determined such that it is also exceeded by all seventh variations, and - wherein, if this is the case, a detection level indication signal is generated and output, which indicates that also metal bodies of the smaller size could be detected. - exciting a magnetic alternating field, - individually moving exemplary test objects without metal body at a defined velocity through the magnetic alternating field, registering first variations of the magnetic alternating field by the exemplary test objects individually moved therethrough, - determining a variation limit for test objects without metal body of a predetermined shape, size and composition using the first variations, - individually moving test objects to be tested through the magnetic alternating field, - registering a second variation of the magnetic alternating field by the respective test object individually moved therethrough, - comparing the second variation to the variation limit, - if the second variation exceeds the variation limit, generating and outputting a metal warning signal, - wherein, in determining the variation limit, at least one third variation, which is one of the first variations or a generalized variation derived from the first variations, is superimposed at different temporal offsets with a first variation function, which corresponds to a fourth variation of the magnetic alternating field when moving the metal body of the predetermined shape, size and composition at the defined velocity through the magnetic alternating field, to provide virtual fifth variations, - wherein the variation limit is determined such that it is exceeded by all fifth variations but none of the first variations, characterized in - that, in determining the variation limit, the at least one third variation is superimposed at the different temporal offsets with a second variation function, which corresponds to a sixth variation of the magnetic alternating field when moving a metal body of the predetermined shape and composition but of a smaller size at the defined velocity through the magnetic alternating field, to provide virtual seventh variations, - wherein it is tested whether the variation limit can be determined such that it is also exceeded by all seventh variations, and - wherein, if this is the case, a detection level indication signal is generated and output, which indicates that also metal bodies of the smaller size could be detected.