Explainer: Silver Bar Markings

Silver bar number 4185, recovered from the wreck of the 1622 Tierra Firme galleon Nuestra Señora de Atocha, was created at the foundry at Potosí, high in the Andes mountains. It bears markings that tell its story, as well as the broader narrative of how the ingots were documented in their journey from the Andes to Spain. The 93 lb ingot was being shipped by Miguel de Munibe, a commercial agent based in Lima. Munibe was on the Atocha and perished when it sank.

Each silver ingot on the 1622 galleons was marked with a series of stamps and inscriptions used to designate, register, and track bullion as it traveled from continent to continent. These various marks corresponded to a written manifest. This document was penned in duplicate, one was sent on the ship with the bar and the other was sent to Spain on a different ship. Upon arrival, each ingot was checked against the manifest and delivered to the proper recipient.

Though the combination of markings on each bar was unique, they adhered to a strict and purposeful system. The functions and meanings of the marks on bar 4185 are as follows:

Key to Silver Bar Markings

1. The MB mark of Miguel de Munibe, shipper of the bar.
2. The symbol of a person named “Ruiz,” the receiver of the bar.
3. The Royal tax stamp, indicating that the proper taxes on the bar’s value had been paid.
4. The Potosí mintmark “P,” alongside the date 1621.
5. Serial Number 4185 in Roman numerals, indicating the bar was the 4185^th ingot produced at Potosí in 1621.
6. The assayer’s “bite,” a small, scooped sample taken to determine the purity of the silver.
7. The purity value in Roman numerals. In this case, 2380 out of a possible 2400, or over 99% silver.
8. Assayer Juan Sanchez Mexia’s stamp certifying the purity of the silver.
9. Obliterated owner’s marks from earlier transactions.
10. The “V” stamp of Atocha silvermaster Jacomo de Vreder, indicating he had received and registered the bar for shipment.