It is quite possible the older 6-pin telegraph circuits on the right were being superceded by the (newer) 10-pin lines on the left when this photo was taken. This main line ran from New York City through Boston, MA and up through Portland, Maine (and discecting to other parts from there...) Western Union was upgrading a lot of their line infrastructure during the 1910s, replacing old 6-pin poles carrying iron wire with new (often cedar, at least here in New England) poles with 10-pin arms, hard-drawn copper wire and double petticoat insulators. Then-new CD 145s and 152s were placed upon the upgraded lines and double-petticoat insulators of former Western Union standards (such as CD 151's, crown-embossed Brookfield CD 145s) from the older circuits were reused if in good condition. A sweet pole find in 1975 was a crown-embossed Brookfield CD 151 by myself and a friend in Wells, ME along this same stretch (about 30 miles south of Portland). I still own the insulator ;-)