In center of the big loop on Silver Zone Pass, there is the grade of a switchback.

The loop is not a true loop like Tehachapi, but rather a horse-shoe where the two ends almost touch. For this description, though, it can be regarded as a U, with the bottom of the U to the north. The right-hand-side of the U (on the west) is the uphill leg.

The upper branch of the switchback comes off of the right-hand side of the U (the uphill leg), and ends at a little hill just above the bottom of the U. It appears that the switchback cuts partway into this hill, to make the tail just a bit longer. The lower branch proceeds from there to end at the left-hand (downhill) side of the U, but it doesn't join the track like the uphill leg does. The switchback grade hits the track of the U at right angles, and at a lower elevation - it can't connect to the existing track, unlike the upper leg of the switchback. There was no evidence of a grade continuing outside the loop, either.

There are cinders at the bottom of the lower switchback leg, and also at the tail track, indicating that this was really used. But when? And for what? Was it just used during construction?