Re: 20-36 dual gauge?

Years ago I knew the owners of the Chollar Mine tour in Virginia City, NV. They had a battery locomotive and end dump ore car to keep the mine cleaned out and make improvements. I remember Chris saying that the trammer actually was set up for multiple gauges, but don't remember how it was done or what their gauge was. I believe a variety of gauges from 18" to 42" were/are common in underground mines. I wonder if the ore cars were brought to the surface by various hoists and then delivered to the smelter? What was the Death Valley "baby gauge"?

I've been trying to figure out the dual gauge switch. While the photo is fantastic and has an unbelievable amount of detail, by the time you zoom in to the switch it's just too grainy. There has to be some switchstands or ground throws in there somewhere. I'm thinking they did this arrangement because they thought it saved money by only having one frog.