TheStreet.com Ratings provides exclusive stock, ETF and mutual fund ratings and commentary based on award-winning, proprietary tools. Its "safety first" approach to investing aims to reduce risk while seeking total return performance. BOSTON ( TheStreet) -- TheStreet.com's stock-rating model upgraded specialty-minerals company Amcol ( ACO) to "buy." The numbers: Third-quarter profit multiplied seven times to $13 million, or 43 cents a share, as revenue fell 25% to $191 million. Amcol's gross margin rose from 29% to 34%, but its operating margin was unchanged at 11%. A quick ratio of 1.9 indicates adequate liquidity. A debt-to-equity ratio of 0.6 is below the industry average, demonstrating restrained leverage. The stock: Amcol is up 39% this year, beating major U.S. indices. The stock trades at a price-to-earnings ratio of 38, a premium to the market and diversified metal and mining peers. Shares pay a 2.5% dividend yield. The model downgraded electric utility Exelon ( EXC) to "hold." The numbers: Third-quarter profit rose 8% to $757 million, or $1.14 a share, as revenue fell 17% to $4.3 billion. Excelon's gross margin jumped from 35% to 44% and its operating margin increased from 27% to 32%. A quick ratio of 1 reflects adequate liquidity. A debt-to-equity ratio of 1 indicates higher-than-ideal leverage. The stock: Exelon has dropped 13% this year, lagging behind major U.S. indices. The stock trades at a price-to-earnings ratio of 12, a discount to the market and utility peers. Shares pay a 4.3% dividend yield. The model upgraded Maxwell Technologies ( MXWL), a maker of energy-storage and power-delivery products, to "hold." The numbers: The company's second-quarter loss widened 7% to $5.3 million, but the loss per share decreased due to a higher share count. Revenue grew 30% to $25 million. Maxwell's gross margin rose from 33% to 42% and its operating margin climbed from negative 21% to negative 4%. The company has an admirable financial position, with $32 million of cash and $19 million of debt.