A great photo of a classic streetcar, but what really sets it apart is the unusually clear view of the plow (behind the front truck) which drew electric power through the conduit slot between the two running rails. Washington DC and Manhattan were the only two significant installations of conduit traction in North America. It was costly to build but spared the street the clutter of overhead wires.

The car does carry a trolley pole, but this was for use in suburban areas where conventional overhead was used.

Car 766 was already an antique when this photo was taken, used only for charters and special trips. It's preserved at the National Capital Trolley Museum, mentioned in a recent Shorpy post.

The pre-PCC 1918 vintage 766 was an older car relegated to excursion only use at the time of this snap. It's currently being restored at the National Capital Trolley Museum: http://www.dctrolley.org/dccollection/27