The Case of the Dyslexic Mint Worker

The Case of the Dyslexic Mint Worker

January 17, 2024

Reversed letters and design elements on silver “cob” coinage produced by the Potosi mint might have been the work of an employee suffering from a reading disorder.

Excerpts by A. Torrey McLean in: Numismatist Vol. 105, no. 6 (June 1992), p. 778-782 ANA 145916

During the period of 1619-22, a worker at the Potosi mint apparently suffered from dyslexia, a reading disorder characterized by impaired ability to interpret spatial relationships or to integrate auditory and visual information. This theory is supported by a number of the surviving coins struck in Potosi during that brief period exhibiting distinctive abnormalities that are unusual even for the crude Spanish colonial silver “cob” coinage of what was then the Viceroyalty of Peru.

The first indication I had of this strange series of cob coinage occurred in 1986 when Louis D. Hudson, a friend and specialist in Latin American coins, showed me a very unusual group of five Potosi cobs struck between 1619 and 1622. Two of these coins had a “P” initial (mintmark of the Potosi mind) that more closely resembled the Greek letter phi ( ) than the normally encountered Roman letter “P,” while the other three had reversed “P” mintmarks. At the time, neither of us could guess why such strange variations of the letter ”P” would have been used repeatedly and on different denominations.

Shortly after, I obtained a Potosi 8-reale cob dated 1622 that exhibited an unusual reversal of portions of the Hapsburg shield on the obverse. At the time, I dismissed this aberration as careless mint work typical of the period, not realizing that it could be related in any way to the unusual mint initials. Subsequently, I studied numismatic references and located enough examples of similar variant designs to conclude that a significant number of these unusual cobs must have been struck in Potosi during a relatively short period. However, I remained at a loss to explain these coins as anything more than products of unskilled die-cutters who inadvertently reversed images by incorrectly copying earlier dies.

Apparently the first person to consider dyslexia as a possible cause of these die variations was Leah L. Miguel, former curator of precious artifacts for Treasure Salvors, Inc. (She was familiar with the symptoms because her dyslexic son frequently wrote letters and numbers backwards.)

The “dyslexic” features of these strange coins fall into three basic categories—mintmark variations, transposed elements of the Hapsburg shield, and the transpositions and reversals within legends and designs outside the shield. Aberrant features are found on cobs assayed by … – Juan Ximenez de Tapia (who used “T” as his assayer’s initial) …



Variations of the “P” mintmark provide the most striking and obvious indication of a dyslexic mint worker, and two such variations within this category have been noted. The rarer of the two is simply a reversed letter “P.” …

…The second and more frequently encountered variation is a reversed letter “P” that has been corrected, resulting in a mintmark that resembles a shortened Greek letter phi. This is probably the result of an attempt to correct the earlier die with the reversed initial, perhaps because of complaints by the authorities…


The second and more complex category of “dyslexic” die variations concerns the placement of elements within the Hapsburg shield, symbol of the reigning monarch of Spain. The most obvious variation is the transposition of the quarters of Castile-Leon and Aragon-Naples-Sicily…


The third possible category of “dyslexic” aberrations is that of transpositions and reversals within the obverse and reverse legends, and transposition of major elements of the design outside the Hapsburg shield.

Since few coins of this period show significant portions of the legend, it is very difficult to document these variations. However, one 8-real cob listed by Dr. Ernesto A. Sellschopp clearly provides an example of exactly what one would expect to find in a “dyslexic” legend – the king’s Latin name “PHILIPVS” spelled with each letter “P” reversed…


After considering these variant designs carefully, several questions remain…In spite of these questions, several facts concerning these unusual designs are undisputed: a relatively short period of time was involved, the nature of the die variations is distinctive, and portions of designs rather than complete designs are reversed. These factors reasonably justify the conclusion that a mint worker at Potosi suffered from dyslexia and that this condition either directly or indirectly resulted in unusual reversals of design elements on cobs during 1619-22 (and perhaps longer)… there is no question that a fascinating – and collectable – series of distinctive, unusual designs exists on many Potosi cobs of this period.




Thanks go to Louis D. Hudson and Leah L. Miguel for their willingness to share their opinions and experiences. Torrey McLean is the State Registrar of North Carolina and resides in a suburb of Raleigh. A former military intelligence officer in the U.S. Army who served in Germany and Vietnam, he was employed by the North Carolina Division of Archives and History for 14 years prior to becoming State Registrar. McLean also is a member of the American Numismatic Society, and has studied and collected Spanish colonial “cob” coins for more than 20 years.