* Reserves body flags 3rd round of auctions in rare stocks release * Sales include 70,000 T aluminium，50,000 T zinc, 30,000 T copper * Aluminium on offer includes tiny batch from 1970s West Germany (Adds details in paras 9-12; updates Shanghai metal prices) Aug 27 (Reuters) - China’s state reserves administration said on Friday it would sell off a total 150,000 tonnes of its strategic metal stockpiles via public bidding on Sept. 1, in the third round of auctions aimed at cooling high prices. The National Food and Strategic Reserves Administration said in three separate notices it would auction 30,000 tonnes of copper, 50,000 tonnes of zinc and 70,000 tonnes of aluminium. The rare series of state reserve sales has so far seen a total of 270,000 tonnes of the three metals released. The last auction on July 29 saw the administration sell 170,000 tonnes of metal, including 90,000 tonnes of aluminium. Some Chinese consultancies had said last week the reserves administration - which had been expected to hold sales every month for the rest of this year - would not release metal stocks in August due to a rise in coronavirus cases. The administration, however, insisted it would keep releasing reserves because prices were still high and causing problems for small and medium-sized enterprises. The bidding is only open to metal processors and manufacturers. Shanghai copper prices closed at 69,130 yuan ($10,664) per tonne on Friday, some 12% below a record 78,560 yuan hit in May, while zinc is down around 5.1% from its May high. Shanghai aluminium, however, hit a 13-year peak on Friday on concerns of tight supply. As with previous auctions, the copper and zinc bidding will be conducted on a China Minmetals Corp platform, while the aluminium will be sold on a portal operated by another state firm, Norinco. Potential bidders can inspect the metal in warehouses on Aug. 31. Almost 4,600 tonnes of the aluminium on offer dates back to the 1970s, having entered storage in 1975-76 after being produced in Canada, Australia, France and - in the case of a tiny batch of 0.89 tonnes - West Germany. The oldest zinc being sold entered storage in 1983 and the oldest copper in 1981. $1 = 6.4841 Chinese yuan Reporting by Tom Daly; editing by Jacqueline Wong and Jason Neely Our Standards: The Thomson Reuters Trust Principles.