In order to track and assess historical processes and cultural dynamics across large areas, the respective chronologies must be reliably correlated. In the late Iron Age in Central Europe, the approaches sometimes diverge widely, a problem that is particularly relevant for the synchronisation of the absolute chronology between La Tène, Jastorf and Przeworsk. This paper examines the central forms to determine the extent to which they can be used for large-scale horizontal alignment. Using the example of the Kostrzewski K and Almgren 18a types of brooches, their synchronisation potential is analysed on the basis of a detailed reconceptualisation of the classification of variants. This reveals remarkable asynchronies and regional variants, which significantly reduce the number of usable brooches. This makes individual variants that connect the north and the La Tène culture, but only occur in a few places in the south, all the more remarkable. It becomes clear that any attempt to harmonise chronological systems requires a detailed analysis of the types used.