The ornamental design for the instrument column, as shown and described.
FIG. 1 is a top, front and left side perspective view of the instrument column according to my new design;
FIG. 2 is an enlarged top plan view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is an enlarged view of the table shown in the broken line box of FIG. 1; and,
FIG. 7 is a top, front and right side perspective view of the instrument column according to my new design and shown in an alternate position.
The uniform broken lines shown in the drawings illustrate portions of the instrument column that form no part of the claimed design. The dash-dot broken lines illustrate boundaries between claimed and unclaimed surfaces which form no part of the claimed design.