The ornamental design for a socketplate for cable drum, as shown and described.
FIG. 1 is a front, right hand side perspective view of a socket plate for cable drum embodying the principles of my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a bottom view thereof;
FIG. 5 is a rear view thereof, the rear view being unadorned and forming no part of the claimed design;
FIG. 6 is a side view thereof as seen from the left hand side of FIG. 2;
FIG. 7 is a side view thereof as seen from the right hand side of FIG. 2; and,
FIG. 8 is a perspective view similar to FIG. 1 with the socket plate shown in a cable drum.
The socket plate for cable drum being shown with the sides and rear in FIGS. 1 and 3-7 in phantom lines and with a cable drum in phantom lines in FIG. 8, the objects in phantom lines forming no part of the claimed design.