A wagonload of new insulators (circa 1910) is being taken from Ventura County Power Co.'s warehouse in Ventura to the site of the construction of the 33,000-volt line to Castaic. The photo was used in the book, Iron Men and Copper Wires. The insulators are similar to M-2870 and are cemented on a heavy metal pin ready for installation. Photo is on page 82 of my book, 2nd edition Multipart Porcelain Insulators.
Southern California Edison Collection of Photographs, Courtesy of the Huntington Library, San Marino, California. Photo (undated) is from the Huntington Digital Library: http://hdl.huntington.org/cdm/singleitem/collection/p16003coll2/id/5748/rec/45