COPCO used the M-2900, M-2926A and M-2927 multiparts on 66kv even though they are only rated for 55kv. The crossarm is wood and the climate is generally dry in this area so that may have been their excuse for under rating the insulator size. Later installations use the normal size 3 part multi. Even newer poles used line posts and of course, the dreaded rubber chicken line posts.