BROKERAGE FIRM UPS STAKE IN ALLEGHENY <AG> The New York brokerage firm of Spear, Leeds and Kellogg told the Securities and Exchange Commission it had increased its preferred stock in Allegheny International Inc to 8.6 pct, from 7 pct. It said it may buy additional shares, but had not decided whether to offer its shares in response to a tender offer by Sunter Acquisition Corp, a unit of First Boston Inc. The brokerage firm said it bought the Allegheny shares March 30-April 2 for 86.50-87.25 dlrs each.