Bright field photomicrograph of an etched polished cross section of a Roman cornu. Grains are quite large (50–100 µm equivalent diameter) and homogeneous in size with a regular polygonal morphology. Thermal twins are frequent, as seen by the thick straight dark lines crossing the grains from one boundary to another. A number of features, including metal composition and microstructure, have proved to be very similar across the five investigated cornua from Pompeii, strongly suggesting that they were made by a single workshop. Very advanced technical skills (notably for tuning) are evident. The sample P20 studied here comes from the pavilion area of Cornu B1, Pompeii, 1st century CE, developed length of the Cornu 366 cm (Museo Archeologico Nazionale di Napoli, registered under #114261 in the January 1884 Pompeii excavation registry). See Caussé, René, Benoît Mille, and Margaux Tansu. 2020. “La facture des trompes: étude acoustique et métallurgique, essai de modélisation.” In Cornua de Pompéi, trompettes romaines de la gladiature, edited by Christophe Vendries, 79–98. Rennes, France: Presses Universitaires de Rennes..