... What if Nic is actually Judas? He made a deal and accepted a coin ... Then with Andriel's help he faked his death by hanging, that's why the noose is so important, and this is how the coins got into circulation...
That...
Uh...
That actually makes a
Hell (in both the "H" and "h" senses of hell) of a lot of sense.
The Bible actually says it: Judas
did make a deal,
did accept the coins.
He made the unholiest deal of all, betraying God to His death.
... along with the 36 other inhabited coins when he betrayed Jesus ...
29 other coins.
Dunno where you got 37 from? Pretty sure you're mistaken.
(minor point; but still)
... When they can get them, the Church tries to keep them locked away. However over time someone gets corrupted and they manage to get into circulation again.
The whole "someone gets corrupted" is I think a common mechanism for coins to get into circulation.
But also: Lash was very clear that she could teach Harry in moments how to summon the coin. I bet that would have been equally true if he had already turned it over to the Church.
I have a WAG that (at least some) Fallen can imprint a Shadow onto a mortal easily, and do so often, usually having half a dozen (or more) Shadows operating at any given moment. These Shadows would mainly serve as "emergency backup" -- any of them can summon the coin out of the Church's clutches. In the meantime, the Shadow earns trust and proves their value by helping the Shadowed host achieve their goals: lots of wealth... lots of hot sexual companions... power & influence... anything they want.
In the final analysis, I think the Denarii are
supposed to be in circulation. They aren't
allowed to languish in Church vaults or other hidden places.