TENDER FOR ALLEGHENY INT'L <AG> UNDERWAY First Boston Inc's <FBC> Sunter Acquisition Corp said it began its previously announced 24.60 dlr per share tender offer for Allegheny International Inc's common stock. The company is also offering 20 dlrs for each 2.19 dlr cumulative preferred share, and 87.50 dlrs for each share of 11.25 dlr convertible preferred stock. The company said the offer and withdrawal rights will expire at midnight April nine unless extended.