Añado la descripción de icollector:
Mexico City, Mexico, uniface cast "10 reales," dated 1611, rare. CT-50; Cayon-4884. 34.5 grams. This odd issue has been pictured in classic Spanish numismatic references as far back as 142 years ago, appearing in Heiss (1869), Vidal Quadras (1892), Ulex (1908) and Dasi (1950), as well as all the most recent ones (Calico, Cayon), so it is accepted as a contemporary issue, especially as all examples are of the same weight and details but with slight differences; but without any official documentation or records, it must have been a provincial or private issue and is usually referred to as "mining currency" or "peso de minas." Like the others, this specimen shows a bold 1611 date, oM mintmark and "REI" (for king?) around a Jerusalem cross, the other side blank, on a thick, octagonal flan with sides hammered in, nicely toned and lightly patinated.