The Peabody Institute at Baltimore's Johns Hopkins University has added another violin to its instrument collection. A 1620 Maggini violin has been donated by Karl Kostoff, a former orchestral musician and a longtime employee of the university's Applied Physics Laboratory. Kostoff, 85, bought the instrument 40 years ago for $9,000. It was recently valued at $350,000. The Peabody's collection also includes a 1702 Rogeri, a 1680 Carlo Tononi and a 1640 Testore.