Poster der BNG und der Staatlichen Münzsammlung München auf dem XXVI Limeskongress, Batumi, Georgien
Abstract:
- The analysis of about 500 Military diplomas showed no major changes in alloy composition
over the 200 years investigated, from ca 60-260 AD. - The manufacturers kept the bronze alloy constantly in a narrow range of 8+ % tin and above
20 % lead. This functional lead bronze alloy must have been chosen to optimize the mass
production process for the metal plates, which are usually between 0,5-2 mm thin, and to allow
engraving of the diploma text on both sides of the plates. - This continuity was kept up by the imperial administration regardless of cost throughout
multiple crises into the middle of the 3rd century AD. - The special alloy of military diplomas seems to differ from other Roman alloys. It also does
not match the alloys of civilian tabulas and bronze finds from Roman camps (Wilkenburg,
Kalkriese, Haltern, Carlisle, Battle of the Harzhorn, etc.) or coins. The color of the military
diplomas was a light red bronze, perhaps to prevent forgeries? - Other functional alloys such as the Weisenau helmet described here also show the high
standards of Roman metallurgy