Wow! Wonderful historical finds! That Magma plate is quite a discovery - Congrats.
For a few months 15 years ago we lived in the Kearny & Christmas Valley areas of Arizona, enjoying hiking several of the mountain & flatland areas. I became more careful after I nearly fell down a mine shaft when ducking behind some bushes to take a leak. This was before I began detecting, but as I was already a rock-hound, I enjoyed finding cool mineral rocks. Also read up a lot on Arizona's mining history, as we also lived & hiked in Bisbee & Sierra Vista for a while. Rugged amazing country! Andi