 The production cost of these new Qianlong Tongbao cash coins was about 15% of the material value and their intrinsic value exceeded their nominal one.Yet in actuality not all provincial mints followed the imperial directive to change the alloy of the coinage and continued to produce the cheaper copper-zinc alloy which was used before.From this period onwards the Ministry of Public Works Mint manufactured 12,490 strings of cash coins annually (with 1,000 cash coins per string).