We recently discussed glass insulators being used on chair legs. This photo from the CD: The Early Days of PG&E, 1891-1926 showing a photo from a 1911 PG&E book (courtesy of SharingHistory.com), clearly shows CD 287 insulators used to insulate two platforms used by operators. Note, too, the two large porcelain insulators at the top right of the photo that are mounted horizontally on a switch. I do not what multipart style they are. The outer skirt is broad and flat with no inner skirts visible or extending below.
The description of the photo is: "Interior of Mountain View sub-station, showing regulators on the left, switch-board in the center, and bank of transformers on the extreme right. In this cut is also shown the systematic arrangement of fire apparatus at one of the fire stations in the sub-station, and which is representative of protection given the Company's properties. This fire station consists of one three gallon chemical extinguisher, six dry powder extinguishers and a nest of three fibre buckets containing dry sand, which is used in smothering possible electrical fires."