I finally got around to driving the Copper Mountain trail. It appears in 3 of my trail books: "Guide to Northern California Backroads & 4-Wheel Drive Trails" by Wells, "High Sierra SUV Trails, Volume 1, The East Side" by Mithcell, and "Sierra Nevada Byways" by Huegel. As you can see in the photos, the trail is pretty easy, mostly class 2 with small spots of class 3. The views are terrific.
Before I drove it, I read the descriptions in each book and decided to use the Wells book while driving it. There was no chance of getting lost since the roads also showed up in my Garmin Nuvi navigation toy. I encountered one other SUV out there (a young couple in an FJ Cruiser) and they were using Mitchell's book.
This trail ascends to the top of Copper Mountain which sits to the west of Mono Lake and just north of Lundy Canyon, offering great views of both.
Here's a google map centered on Copper Mountain.