FIG. 1 is a top plan view of a top portion of a spring core showing our design;
FIG. 2 is an enlarged fragmentary view taken from the top left corner in FIG. 1;
FIG. 3 is a side elevational view;
FIG. 4 is an enlarged fragmentary view taken from the far left in FIG. 3;
FIG. 5 is a side elevational view, showing the side opposite that shown in FIG. 3;
FIG. 6 is an enlarged fragmentary view taken from the far left in FIG. 5;
FIG. 7 is an end elevational view;
FIG. 8 is a enlarged fragmentary view taken from the far left in FIG. 7;
FIG. 9 is an end elevational view showing the end opposite that shown in FIG. 7; and,
FIG. 10 is an enlarged fragmentary view taken from the far right in FIG. 9.
The broken lines are for environmental purposes only and form no part of the claimed design.