Interesting find.. Those Garrand clips bring to mind the days when I was first issued my M-1 (it was well worn by then (1955).
The loading was accomplished by risking an "M-1 thumb", which could be avoided by holding the operating rod back with the edge of the hand. The clips were very springy spring steel, which when empty and ejected gave a very audible "ping"..
I often wondered if a battle experienced enemy would relate this to a momentarily empty rifle.
While very interesting, I am not surprised that these items were not found by this time, particularly in a remote area. I find that some relics remain undiscovered for a long time.
My son was working full time with a Christian youth ministry back in the mid 1980s. At one point he ws chaperoning a large group of the young people attending a rally held on the National Mall, the grassy expanse which runs between the Lincoln Memorial and the capitol building. This area it seems is very often covered with people..involved in either rallys or "demonstrations"..
At one point, while seated under a large tree he rested his hand on the grass, palm downward. Feeling what he took to be a pebble, he picked it up and discovered a very nice minne-ball. It was evidently left there when federal troops guarding the capitol were bivouaced there during the 1861-1865 fracas..