SHEARSON HAS 5.4 PCT OF CHICAGO MILWAUKEE <CHG> Shearson Lehman Brothers Inc, the brokerage subsidiary of American Express Co <AXP>, said it has acquired 131,300 shares of Chicago Milwaukee Corp, or 5.4 pct of its total outstanding common stock. In a filing with the Securities and Exchange Commission, Shearson said it bought the stake for 18.8 mln dlrs for investment purposes and has no intention of seeking control of the company.