Rather my thought as well. Especially given the strange way that he's able to pool and manage magic through his hands, without nerve damage, due to to the genetics he inherited from his sire. And remember also, he doesn't use heavy or mostly metallic armor, because it interferes with his magic, but leather and cloth armor seemingly doesn't inhibit it at all. And there's also the bit where MC suddenly realizes he's an idiot for having stored the communication coin in his storage dimension thing instead of a pocket or pouch in his clothes or armor. Given all of these factors, it just makes sense that it only needs to be generally on his person, rather than it being required to make literal unobstructed physical skin contact.
Plus, notwithstanding MC's particular abilities, I'm sure his companions generally need their hands free for other things, as well. Especially where combat is concerned. I doubt they are walking around with the coin in the palm of their hand all the time, rather than in a pocket or pouch. Ergo, it must be reasonably inferred that the artifact only needs to be on the body and fairly close to the skin, because it simply doesn't make sense otherwise. As an experienced warrior myself, it's just reflex and habit to always keep my hands as free as possible in order to quickly draw weapons and fight. If I have to hold to hold a dog leash or flashlight, for example, it goes in my non-dominant hand, and I generally prefer instead to attach the leash to my belt, or loop it around my body, or something, and use a weapon-mounted light instead of holding a light in one hand. It stands to reason that the same habits and mindset would hold true of MC's companions, as they are also trained and experienced combatants. No experienced warrior is gonna be walking around with a coin in their hand all the time, if they can help it. Especially since they don't have the benefits of modern technology and convenience, and therefore need their hands free for even more reasons.
