The ornamental design for a lampbase, as shown and described.
FIG. 1 is a front elevational view of a lamp base showing my new design;
FIG. 2 is a left side elevational view thereof; and
FIG. 3 is a perspective view thereof on an enlarged scale.
The lamp shade, harp, light bulb and light socket of FIGS. 1 and 2, and the
harp, light bulb and light socket of FIG. 3 shown in dotted outline form
are environmental structure and are not part of my design sought to be
patented.