Material description of a unique relief fibula from Poland

A unique relief fibula dated to the Migration Period (first half of the sixth century) was found in Radziejow, Poland. This stray find changes previous opinions on the lack of settlement in central Poland at that time. As the find is the only one of such type in Poland, a special attention was paid to possible analogies, mainly finds from Scandinavia and Western Europe. The fibula underwent technological analyses in order to reveal its technology of manufacture. For this purpose, the chemical and elemental composition of the alloy was studied. Several physico-chemical complementary techniques such as optical microscopy (OM), scanning electron microscopy with energy dispersive X-ray (SEM–EDX) spectroscopy, energy dispersive X-ray fluorescence (ED-XRF) analysis, X-ray diffraction (XRD) analysis and micro-hardness testing (HV0.2) were used to study the technology of the find. The investigations revealed that this artefact was made from brass (4–17 wt% Zn) with an admixture of Sn (2–12 wt%). Two technologies were used: casting for the bow and forming for the part with the axle of the spring. The artefact’s surface was tinned in the hot-dipping process. The physical structural analyses demonstrated that the artefact was cast and ornamented by surface stamping under a relatively low temperature (about 500 °C).