The ornamental design for a down-socket adaptor for a portable harp systemlamp, as shown and described.
FIG. 1 is perspective view of the down-socket adaptor for a portable harp system lamp embodying our design;
FIG. 2 is a front elevational view of the adaptor of FIG. 1, with the rear elevational view being a mirror image thereof;
FIG. 3 is a left side elevational view thereof, with the right side elevational view being a mirror image thereof;
FIG. 4 is a top plan view thereof; and,
FIG. 5 is a bottom plan view thereof.
The broken line illustration of exemplary light bulbs in the down-sockets of the design are environmental and are not part of the adaptor design sought to be patented.