The ornamental design for a clock, substantially as shown and described.
FIG. 1 is a front elevation of a clock showing my new design in which the
numerals are arranged in vertical columns, the rear being substantially
plain and unornamented;
FIG. 2 is a perspective view of the clock in FIG. 1 showing the right side
and top, the left side and bottom being mirror images of the right side
and top respectively, and
FIG. 3 is a front elevation of another embodiment of my clock in which the
numerals are arranged in horizontal rows, the rear being substantially
plain and unornamented, the sides being substantially identical to the top
and bottom of the clock in FIGS. 1 and 2, and the top and bottom being
substantially identical to the sides of the clock in FIGS. 1 and 2.