IF ANY two partners can be said to symbolize a firm, S. Leslie Misrock and Jonathan A. Marshall symbolized New York’s Pennie & Edmonds. Both top trial lawyers in the field of intellectual property and patent, Messrs. Misrock and Marshall also spent a combined 75-year law career building the firm into a 200-lawyer powerhouse among IP boutiques.

Mr. Misrock’s death last August at the age of 73 deprived Pennie & Edmonds of one of its stalwarts. Now it is preparing to lose the other, albeit for a very different reason. Last week, Mr. Marshall, senior partner and head of the firm’s litigation department, announced he would be leaving Pennie & Edmonds after 36 years to become a partner at 950-lawyer Weil, Gotshal & Manges at the end of the month.