III the design was changed and the pillars were moved to the reverse of the coin while of the Spanish coat-of-arms were superseded by a portrait of the reigning monarch, because of this these coins were known as "Carolus dollars" or columnarius ("with columns") in the West, while the Chinese referred to them as Zhuyan (柱洋, "pillar dollar"). Additionally on some Carolus dollars the inscription "PLVS VLTRA" was found. The Spanish Carolus dollars always had a standard weight of 27.468 grams, while their silver content was lowered from 0.93955 to a purity of only 0.902. From the year 1732 onwards these coins were manufactured in Mexico City and other parts of Spanish America. The portraits of kings Charles III and Charles IV (with the "IV" written as "IIII") were featured on these coins, the Chinese referred to the Latin numeral "I" as "工" causing the silver coins of Charles III to be known as Sangong (三工) while those produced under the reign of Charles IV were known as Sigong (四工) coins. Additionally the depiction of the reigning Spanish monarch inspired the Chinese people to refer these Carolus dollars as Fotou Yang (佛頭洋, "Buddha-head dollar"). The Carolus dollar came in the denominations of ½ real, 1 real, 2 reales, 4 reales, and 8 reales of which the highest denomination had a diameter of forty millimeters and a thickness of 2.5 millimeters. All Carolus dollars issued under the reign of Charles III to China were produced in the year 1790 while those under Charles IV all date from 1804 onwards. In daily exchange the Chinese rated the 8 reales Carolus dollars at 0.73 Kuping Tael and was one of the most important forms of exchange, the Treaty of Nanking that ended the First Opium War had its payments measured in Spanish Carolus dollars. According to estimates by the British East India Company the Qing dynasty imported 68,000,000 Taels worth of foreign silver coins between the years 1681 and 1833, this sets China's imports over 100,000,000 foreign silver coins with the bulk of these being Spanish Carolus dollars produced in Spanish America that entered China through trade. The Chinese preference of the old Spanish Carolus dollars over newer European silver coinage, Mexican real, Peruvian real (later the Peruvian sol, and the Bolivian sol (later the Bolivian boliviano) was considered to be "unjustified" by many foreign powers, it took the combined diplomatic interventions of