Editor's Note: This is the conclusion of the series on analysts' ratings of metal stocks. Earlier articles analyze the ratings of copper and aluminum stocks and steel stocks.

NEW YORK ( TheStreet)- The wide disparity between upgrades and downgrades for gold and silver stocks may continue for the remainder of 2010, providing an opportunity to play the long-short strategy with no sector risk.

Silver stocks could receive higher upgrades than gold stocks on the robust outlook for the white metal. Meanwhile, upgrades for palladium stocks may gain momentum when the metal starts recovering from the recent losses, offering buying opportunities.

During the past six months, Hecla Mining ( HL - Get Report), the largest U.S. producer of silver, received the highest upgrades among precious metal stocks on the company's low-cash costs and a positive outlook for silver.

Silver Wheaton ( SLW), top silver stock pick for more than four months, received upgrades during the second quarter due to the 13 agreements that allowed the company to purchase some or all of its production at low fixed costs.

Stillwater Mining ( SWC) and North American Palladium ( PAL), two palladium stock picks for more than four months, were analysts' favorites for upgrades during the first half of the year on the robust outlook for palladium.

Among gold stocks, Lihir Gold ( LIHR) received the highest upgrades among industry peers in the past six months. During May, the company merged with Australia's Newcrest Mining. Meanwhile, South Africa's Harmony Gold Mining ( HMY) received the highest downgrades due to operational and safety issues.

Among major gold producers, Goldcorp ( GG) received marginal upgrades against marginal downgrades for Barrick Gold ( ABX) and Newmont Mining ( NEM - Get Report).

Karvy Global Services (www.karvyglobal.com), a subsidiary of the Karvy group (www.karvy.com), provides specialized research in asset classes including stocks, mutual funds and insurance to leading Wall Street firms.