Tracing socioeconomic change and emerging elites in 4th-3rd century BCE: Metalwork from the Amber Road Corridor.

Leaded bronze ornaments of the La Tène period provide a key lens on how technological innovation intersected with social and economic change in Iron Age Central Europe. In the 4th-3rd centuries BCE, the Middle Danube formed a major communication corridor between the Balkans and the Transalpine zone. Copper-alloy personal ornaments became central to changing expressions of identity and status, while also reflecting shifts in alloy recipes, raw-material procurement, and craft organisation. A major 3rd-century BCE development was the widespread adoption of leaded bronze, well suited to casting high-relief "Plastic-Style" ornamentation. It remains debated whether this innovation was introduced primarily through emergent agglomeration sites or developed within established local communities embedded in regional networks. We address this question through lead isotope and trace-element analyses of copper-alloy ornaments from 4th-3rd century BCE cemeteries in Bohemia and Moravia, compared with material from the open industrial agglomeration of Němčice nad Hanou. Lead isotope ratios are used to assess metal provenance, while trace-element compositions characterise alloying and casting practices. These data are integrated with chronological, typological, spatial, and decorative evidence, using KDE-based matching, conventional isotopic plots, and multivariate trace-element analysis. The results show a diachronic shift from heterogeneous 4th-century BCE alloying to more standardised leaded bronze recipes in the 3rd century BCE. This technological regime combined improved castability, reduced tin demand through lead addition, and the visual demands of Plastic-Style ornamentation, producing a prestige-coded but widely circulating "bulk luxury" commodity. Lead isotope signatures indicate increasingly structured supply chains, including recurrent use of lead sources consistent with central and western German deposits. Overlaps between cemetery assemblages and Němčice suggest that agglomerations scaled and integrated innovations already present in community-based production rather than initiating them. We argue that rural cemetery communities were active arenas of metallurgical innovation, and that 3rd-century BCE agglomerations functioned as accelerators of locally rooted technological and social trends.