Acquisitions of the Spanish Tumbaga Bars

by Robert Hoge

The Society has recently obtained four particularly interesting and historically significant specimens of 16th century would-be minting material. These items are typical examples of a truly remarkable find: precious-metal bars demonstrating stages of metal-working/minting technology in the context of one of the world’s greatest cross-cultural upheavals, the Spanish conquest of the Americas. Among the very few items that have been selected for acquisition in recent years through designated funds, the bars were acquired at a favorable price through specialist dealer, Daniel Frank Sedwick. The Society continues to seek patron-sponsors for these and other prospective purchases.


One of the Tumbaga bars acquired recently for the collection.

During the 1992 season of its licensed salvage work off the coast of Grand Bahama Island, the Marex Corporation located the remains of one or more shipwrecks dating from the very early period of Spanish conquest and colonization in the New World. Among the artifacts recovered from the remains of a vessel appearing to date from the third decade of the 16th century were approximately 200 cast slabs of precious metal matching descriptions of tumbaga bars mentioned in contemporary references. These remarkable finds, which represent some of the oldest known examples of the vast treasures seized by the conquistadores, provide a glimpse into the first stages of Colonial Spanish metallurgy which culminated in the establishment of the great mint of Mexico in 1536.

The ANS’ four bars have considerable information to reveal to us about the practices and expectations of those who were handling and dealing in bullion at the time of the Renaissance. While the name of the sunken ship, which once carried them, has yet to be conclusively determined, 153 of the tumbaga bars were conserved and analyzed by Douglas R. Armstrong (Tumbaga Silver for Charles V of the Holy Roman Empire, Palm Bay, F., 1993). The term tumbaga designates a varying mixture (not, properly-speaking, an “alloy”) of gold/silver with a relatively high proportion of copper as well as other elements present. Armstrong catalogued the bars in terms of their actual weights, the original markings discernable upon them, and any other observable features. Some showed traces of the melted American aboriginal figurines from which the bars (lingotes, in Spanish) were cast.

Many of the bars were subjected to modern analytical tests which revealed that the old Spanish assays, as shown by the surviving punch-marks applied by the foundry’s workmen, were in general surprisingly accurate in terms of the silver fineness (although they did not identify the presence or proportion of gold in the mixtures). The original assaying was accomplished by chiseling off a small corner (a “bite”; in Spanish, bocado) of each bar and then submitting it to a cupellation process. The theoretical purity (in Spanish, ley) was shown by stamping onto the bar a numeral indicating the parts per 2400 of silver content. The numbering system was that of the Western tradition—the Medieval Spanish version of the familiar Roman numerals (e.g., whereas “IU” or “IV” or “Y” was used instead of “M” to write “1000” and the “D” for “500” is of a cursive form, “L” equals “50”; “X” equals 10, etc.). Most of the bars averaged around 50% pure and weighed five to 10 lbs. The bars also bear impressions of the monarch’s official tax collector. These were imparted by circular, coin-like dies inscribed CAROLVS IMPERATOR.

A number of the bars carried a mark of a capital “B” next to a “V” with a superscript “o”. This punch has been attributed to Bernardino Vasquez de Tapia, who is known to have been in the employ of none other than Hernan Cortes, the conqueror of the Aztec empire. The markings of other tesoreros or ensayadores are as yet unattributed. The four bars are fascinating objects, which will be superb additions to future exhibitions. The avoirdupois weight, silver fineness expressed in parts per 2400 (ley) and assayers’ marks of the four bars are given below.

—11.39 lbs., 1500, Io/N; below, DGBCA with a macron above the CA

—12.29 lbs., 1310, mark illegible (a fragment of per mineralized fabric adheres to the lower surface).

—15.70 lbs., 1500, Io/N; below, DGBCA with a macron above the CA (a small, thin sheet of silver is embedded on the top).

—23.08 lbs., 1540, Bo/V