SHANGHAI, Sept. 21 (SMM) –Shanghai spot copper offers were quoted between discounts of negative RMB 50/mt and premiums of positive RMB 50/mt today. Traded prices for standard-quality copper were between RMB 62,600-62,900/mt, and RMB 62,700-63,100/mt for high-quality copper. The latest announced HSBC PMI data continued to improve, and SHFE copper prices moved higher after a low open, which helped low sentiment in the spot market ease. Cargo-holders held premiums firm in the morning business, but as SHFE copper prices increased rapidly, downstream producer buying interest was depressed. As a result, spot copper premiums fell rapidly, but traded prices surged. Market surpluses were still more pronounced, and market transactions were hampered at the highs.