Elton Gish posted two photos of Fred Locke gutter tops (M-2795) being assembled somewhere in California possibly Oakland, CA. The weblinks to the two photos are posted below:

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Using Paul Greaves estimated date of insulator assembly 1900-1901 and the visual landmarks I could identify in the photos: the lumber yard near the fence line, the location near the water body, the railroad trestles in the background and more importantly the two gas holders (gasometers) on the adjacent property, I was able to pinpoint the location of the assembly yard using the Sanborn Fire Insurance Maps of Oakland, CA archived in the History Room of the Oakland Public Library. The staff of the History Room were a big help in pointing me in the right direction. The particular Sanborn Map is dated 1902 and corrected to 1910. At the right top of the map you can see the two gasometers of the Pacific Gas & Electric Company Water Gas Plant. At the bottom left is the Pacific Coast Lumber & Mill Company. The gutter top assembly yard occupied the property between the two businesses at the T intersection of First Street and Castro Street in Oakland, CA next to the Oakland Inner Harbor.

Here is what the property looks like nowadays [id=431050079]