As stated in the subsequent photograph (click "Previous") I am not sure what types of insulators were originally used along the many openwire trolley cable routes that transversed (as many still do) throughout the city. Side-tie (not cable-top) insulators (looking like a scaled-down CD 140) made of bakelite accomodating standard one-inch pins were employed in rather large numbers and some can still be seen in service today. Examples of the latter were lettered J.M. Anderson Co. up on the inside right around the pinhole base. These could have been the original insulators if bakelite insulators for heavy duty service were produced in the teens or before.