My solution for #1 - not sure if it is correct. I didn't expect that two locks could fit in the clasp. Person #2 sends the safe back to Person #1. It has not

My solution for #1 - not sure if it is correct. I didn't expect that two locks could fit in the clasp. Person #2 sends the safe back to Person #1. It has nothing in it. Person #1 locks his own safe to the safe of person #2, making sure the clasp of his safe is over the latch pin of the second safe. Again he sends it back with nothing in it. Person #2 repeats this; now you have two safes locked together (with the latch pin being on top of opposite clasps). He sends the safe back to person #1. Person #1 unlocks his lock, puts the amulet inside, and locks it again. He sends it back. Person #2 unlocks the other side, and now has both safes, plus the amulet.