Abstract: An identification system comprising a plurality of differently frequency coded markings including mechanical vibrating means, and a detector device for detecting the frequency or combination of frequencies of the vibrating means. The vibrating means of the various markings are preferably made from identical comb-like members having teeth which are vibratory with different natural frequencies and of the type used in small music boxes. The different frequency codes may then be obtained by removing teeth in different combinations from the members used in the various markings. The markings may, for example, be arranged on dairy cattle, and the identification system may then be used in connection with a milk sampling system.