MADISON, Wis. A retired University of Wisconsin historian noted for his research into the Watergate scandal pleaded no contest today to threatening to blow up a health insurance building. Seventy-one-year-old Stanley Kutler entered the plea in Dane County Circuit Court to a disorderly conduct charge arising from a phone call with his insurance company. He's best known for his successful 21-year fight to obtain President Nixon's secret tapes, Judge Patrick Fiedler fined Kutler 50 dollars and imposed 149 dollars in court costs. The case hinges on an April 26th phone call between Kutler and Dean Health over a billing dispute.