Marketing Services Group Inc. bought The Coolidge Co., a list management and brokerage firm that specializes in publishing and fundraising, for an undisclosed sum on March 31. Richard Steeg, who has owned New York-based The Coolidge Co. since 1987, said his decision was framed by MSGi’s ability to bring to the table technological resources, such as Internet and e-mail capabilities and modeling programs, that The Coolidge Co. did not offer its clients. While he cautioned that all plans are preliminary and in flux, Steeg said he expects to continue as president of the company. The firm, which generated $12 million in revenue in 1999, currently employs about 30 employees. Downsizing is not expected because of the acquisition and the company will relocate its offices this summer from 25 West 43rd Street to MSGi headquarters at 7th Avenue and 29th Street. The New York-based company was originally founded by Marci Coolidge in 1957 and owned by her until her retirement in 1969.