Bram, Hrafn
Bram, as you hold the sundial coin, and Hraefn mentions magic, you suddenly think about how magical items work. While there is no real way to know when a magical device will expend the last of its energy, you imagine this tiny coin as a marker to the magic left in the device.
Holding it, you both get the sensation that you are holding something akin to a hand-crossbow, as the grip has a tiny bit of movement not unlike the trigger of the crossbow. Surmising, you think that were you to have a different coin, one where the thin line were not on the left, perhaps you might make it work.
OOC:
In lieu of Bram's excellent arcana check, along with Hraefn's help, I figured you could probably deduce as much about the two items.