The ornamental design for a supportbase of a stand for electronic game machine, as shown and described.
FIG. 1 is a front, top and right perspective view of a support base of a stand for electronic game machine showing our new design;
FIG. 2 is a rear, bottom and left perspective view thereof;
FIG. 3 is a top plan view thereof;
FIG. 4 is a bottom plan view thereof;
FIG. 5 is a front view thereof;
FIG. 6 is a rear view thereof;
FIG. 7 is a right side view thereof, a left side view being a mirror image thereof;
FIG. 8 is a first reference perspective view showing a state that a stand for electronic game machine is attached onto this support base while viewed from the front, top and right sides;
FIG. 9 is a second reference perspective view showing the state that the stand for electronic game machine is attached onto the support base while viewed from the rear, bottom and left sides;
FIG. 10 is a third reference perspective view showing a state that an electronic game machine is put on the stand attached onto the support base while viewed from the front, top and right sides; and,
FIG. 11 is a fourth reference perspective view showing the state that the electronic game machine is put on the stand attached onto the support base while viewed from the rear, bottom and left sides.
The broken lines showing the stand and electronic game machine are for illustrative purposes only and form no part of the claimed designed.