A compound hook variation on the hook-jaw pipe wrench theme, evolved from Anderson's 1886 patent no 340,410. The end of the lever acts as a cam to wrap the jaw segments around the work piece. A spring holds the jaws closed. The jaw pivot can be shifted in a slot for size adjustment.
Ken Cope's "American Wrench Makers 1830-1930" notes Anderson was advertising the wrench in 1887.