The ornamental design for a lampbase, as shown and described.
FIG. 1 is a perspective view of the lamp base showing my new design; and,
FIG. 2 is a front elevation view of the lamp base of FIG. 1.
Features shown in broken lines are shown for environment only and do not
form a part of the design claimed. The bottom and top of the lamp base of
FIGS. 1 and 2 are without adornment, are not a part of my ornamental
design and are not separately shown in the drawings. The left, right and
rear elevations are identical to FIG. 2, and so are not separately shown.