A comment an an answer of mine on another question made my wonder about the iron coins used by the Faceless Men, one of which was given by Jaqen H'ghar to Arya.
Was the iron coin given by Jaqen H'ghar to Arya regular Braavosi currency? Or were they a different kind, minted just by/for the Faceless Men as a mean to let them being recognized when they wanted to?
I've always assumed that the Faceless Men used their own coins, without any legal value and distinct for the regular Bravoosi currency; my rationale is that regular currency is used by anyone and is too much widespread to be instantly recognized as a symbol of the Faceless Men, like the sailor to whom Arya shows his coin:
"Wait," Arya said suddenly. "I have something else." She had stuffed it down inside her smallclothes to keep it safe, so she had to dig deep to find it, while the oarsmen laughed and the captain lingered with obvious impatience. "One more silver will make no difference, child," he finally said.
"It's not silver." Her fingers closed on it. "It's iron. Here." She pressed it into his hand, the small black iron coin that Jaqen H'ghar had given her, so worn the man whose head it bore had no features. It's probably worthless, but...
The captain turned it over and blinked at it, then looked at her again. "This... how... ?"
Jaqen said to say the words too. Arya crossed her arms against her chest. "Valar morghulis," she said, as loud as if she'd known what it meant.
"Valar dohaeris," he replied, touching his brow with two fingers. "Of course you shall have a cabin."
A Storm of Swords - Arya XIII
From this passage, it seems to me that the captain is somewhat shocked to see that iron coin, but he is from Braavos, so the mere sight of an iron coin should not be a great surprise to him; but he is "bought" only after Arya say the words, so the whole passage instead of clarifying the situation, gives me even more doubts about the whole subject.
Like, I said, I tend to support the hypothesis that the coins fo the Faceless Men are not regular currency, but I don't have any official reference to support this opinion of mine; for what I know it could be just an assumption made without any established fact.
The only references that I was able to collect are that Arya's coin (given by a Faceless Man) was
a piece of iron no larger than a penny and rusted along the rim. One side had writing on it, queer words she could not read. The other showed a man's head, but so worn that all his features had rubbed off.
A Clash of Kings - Arya X
and about Braavosi currency
Yet they brought him money: leather purses plump with gold and silver and the square iron coins of Braavos.
A Dance with Dragons - The Ugly Little Girl
The World of Ice & Fire book has pictures of both of these coins and they seem to be two different things, but they are both depicted as round coins, and we know that the Bravoosi currency is made of square coins, so I'm inclined to consider these illustrations as inaccurate and to not use them as a solid and valid reference.
So, do the Faceless Men use their own distinct iron coins, or just the regular Braavosi currency?
Please note that I'm only interested in answers about the books, not about the TV show.