Nicely written, but to me, the most parsimonious explanation under the assumption that these are "nuts and bolts" objects not belonging to any Nation is that they are from here, and likely coming out of the oceans. I leave to you the choice of your favourite scenario. Just want to highlight that life on Earth has been going on for billion of years, that the bottom of the oceans is less known than the surface of Mars, and that there are 3-4 satellites with large bodies of water in the Solar System of which we know very little about.