This is a portable transformer rack on skids that powered a gold dredge at Arapahoe Bar, on Clear Creek just east of Golden. Taken circa 1920, based on all the other identifiable photos in the album. Note the three nice U-928 Boch's Patent insulators on the incoming lines. Check the next couple pictures for the interior and the dredge it powers.

From an old Denver Gas & Electric Light Co. photo, taken from a Public Service Co. album.