This copper-alloy disc bears a strong similarity to artifacts from the Chimú culture of northern Peru, 900-1470 CE, such as this example in the Metropolitan Museum of Art:
Northern Peruvian artisans typically worked with copper-arsenic alloys. These alloys are stronger, and easier to cast than copper alone. The process for making copper-arsenic alloy begins with burning charcoal in the bottom of a furnace bowl. Ores were crushed and mixed to make a smelting charge. By blowing through tubes into the furnace, artisans increased the heat in the furnace. However, it was not enough to liquify the charge, and produced prills, or droplets of pure metal, that were collected, and most likely remelted and made into small ingots (Shimada and Merkel 82-83).
Shimada, Izumi, and John F. Merkel. “Copper-Alloy Metallurgy in Ancient Peru.” Scientific American, vol. 265, no. 1, 1991, pp. 80–87. JSTOR, www.jstor.org/stable/24936982. Accessed 15 Apr. 2020.