string of 1000 bronze cash coins equated to a single tael of silver. The Shunzhi Emperor created the Ministry of Revenue and the Ministry of Public Works in Beijing to oversee the casting of bronze cash coins, these ministries produced 400,000 strings of cash coins annually. Later the Shunzhi Emperor ordered military garrisons to start minting their own coinage, and though the official weight for cash coins was first set at 1 qián, in 1645 this increased to 1.2 qián, and by 1651 this had become 1.25 qián. In 1660 the order was given to re-open provincial mints and have them cast their mint names in Manchu script. The standard copper-alloy was 60% copper and 40% lead and/or zinc, yet diverse market conditions dictated what would be the de facto composition. This official composition was officially changed over time, initially it was at a ratio of 3:2 (3 parts copper to 2 parts lead and zinc). The coins produced under the Shunzhi Emperor were modeled after Tang dynasty Kai Yuan Tong Bao coins, as well as early Ming dynasty coins, and have a Chinese mint mark on their reverses these were produced from 1644 until 1661, though these coins had a large range of mint marks from various provinces all over China, from 1644 until 1645 there were also Shùn Zhì Tōng Bǎo (順|治通寶) coins being cast with blank reverses. Kangxi era Yongzheng era Under the Yongzheng Emperor various measures were undertaken to ensure a vast supply of cash coins, though the weight was increased to 1.4 qián per wén, the copper content was lowered from 60% to 50% in 1727. In 1726 the Ministry of Revenue was split into 4 agencies each named after a wind direction, and in 1728 all provincial mints were ordered to open again as only the mint of Yunnan was operating prior to this order, and finally in 1728 the Ministry of Public Works mint was split into a "new Ministry of Public Works mint", and an "old Ministry of Public Works mint". Though by 1733 the Qing government realised that the costs of making standard cash coins at a weight of 1.4 qián was too much, so they lowered it back to 1.2 qián. In 1725 the province of Yunnan had 47 operating furnaces. In 1726 the governour of Yunnan, Ortai made the province's coin minting industry more profitable by implementing new systems