The IK numbers serve to uniquely identify the central images on a gold bracteate.
They were assigned during the compilation of the Iconographic Catalogue and are an important tool for identifying specific images resp. dies. The number refers to the die (matrice) used to mint the bracteate. Many gold sheets could be minted using the same die, which means that they all bear the same IK number. However, if they come from different find spots, they are distinguished from each other by an additional appended number. Example: There are die-identical bracteates from the two hoards found in Darum and Skonager. They bear the same IK number, namely IK 41,1 Darum and IK 41,2 Skonager.
However, if several bracteates of the same model originate from the same find spot, they all bear the same IK number. In order to be able to describe these individual specimens separately, they are designated with an additional, adjusted number after an underscore: IK 41,1_1 Darum; IK 41,1_2 Darum, etc.
Unfortunately, in the original catalogue there are exceptions to the systematic assignment of IK numbers. A few non-die-identical images bear the same IK number because their central images are very similar to each other. Example: IK 51,1 is not die-identical with IK 51,2 and IK 51,3. Such irregularities were eliminated in the course of research.