This is another good example of very early telephone openwire construction here in New England. The top crossarm has always been nicknamed as an "alley arm" so that there would be physical clearance from any adjacent buildings, structures, etc., behind the pole. It was also customary (and standard practice) to install such protruding crossarms along heavily treed open-wire phone routes so that the foliage interference with the bare-wire phone circuits would be minimized. Many such "alley arms" were re-bored standard crossarms such that their pole mounting was adjacent to the arm's end and almost always supported by a long angle-brace at a 45-degree angle as you see here.