There were ten coins made, yet only three coins accounted for, right? That leaves seven left.
Okay, Sleepy Hollow should have a few of them used by Henry... That should at least leave out three to five of them unaccounted for.
Maybe a few of them were mixed in the gold bars aboard the Antonio Graza in the 2004 film Ghost Ship? I know it's not possible, and both timeline and story don't match. But still, this could be a fun idea. Zakynthos coin gold mixed in those unmarked Aurum(Gold) bars, causing all people aboard the ship - passengers, officers, crew members, even performers - to turn on each other. Rat poison in passengers' soup, dance floor bisecting, poolside massacre and the reapings for Jack Ferriman... all of them - under the influence of the remaining coins? And not only the Graza, but also the Lorelei, and every ship before that... all of them, done by the gold bars infused with gold from those coins?