Triunfo (LO site), Ventura County, California, Elevation = 2658 ft.

Located in the Santa Monica Mountains National Recreation Area

There was a lookout at this site prior to 1935. The lookout cab could have been on top of this elevated base. I have never seen a base like this used for any other lookout. It could have been erected later for some other purpose. Article on a fire near the lookout.
A photo of Triunfo Pass benchmark which is southwest of the structure. Thanks to Greg Sweel who found this on May 27, 2017 and took the photo.