The ornamental design for a geometricform for a lamp base or similar article, as shown and described.
FIG. 1 is a perspective view of a geometric form for a lamp base or similar article of my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a back view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The dominant characteristics of the present geometric form for a lamp base or similar article shows a cubical spiral repeating pattern in a clockwise and/or counterclockwise direction which expresses positive/negative space in a counter balanced manner.
The broken lines shown in the figures are for illustrative purposes only and form no part of the claimed design.