"In the networks presented below, each individual brooch is conceived as a ‘node’, and each stylistic similarity with another item is conceived as connection, or an ‘edge’, whose ‘strength’ varies according to the measure of that similarity (for terminology see Brughmans 2012 and Collar et al. 2015). In order to perform such an analysis, each object was divided into a number of fields supplied by the components of the overall design: the headplate outer frame, inner frame and central panel; the bow; the lappets; the lobes; the foot; and the terminal, as illustrated in Fig. 4. Because their form defines these fields, they will be referred to as ‘formal components’. Not all examples, even if they were complete, necessarily possessed all eight of these formal components, but this is not important, as it permits only minor asymmetries in the data. This division permits a maximum number of eight possible counts on which any number of brooches can be compared, providing a score between one and eight for the strength of the relationship between any two brooches. In other words, the strength of each ‘edge’ can vary between one and eight, where eight is the strongest and will be coloured darkest in the following diagrams. With this basic structure defined, the stylistic varieties of each formal component were classified according to their design, based on the presence of a particular ‘motif’. While there is not room here to detail every motif, a small number of illustrative examples are given in Fig. 4, their quantities are summarised in Table 2 and the classificatory data is included in full in the electronic supplementary material (Online Resource 1). Figure 5 illustrates the range of variation within a very small sample of the motif classifications. A total of 288 motifs were designated across all eight formal components, each of which occurred on at least two brooches in the sample of 408 complete and unique items. As can be seen, some formal components exhibited more variation than others, with the central panel of the headplates being particularly open to experimentation, and lobes and terminals being decorated using a smaller repertoire of motifs."