Symbolism, Imagery, Allegory
We couldn't possibly cite every use of coins in the poem, but we're here to tell you to be on the lookout because coins are an important image here. From Achille's understandable obsession with them (because he doesn't have enough) to the "tugs chirring up a devalued empire/as the coins of their wake passed the Houses of Parliament" (XXXVIII.ii.195) spotted by Omeros on the banks of the Thames, coins represent not just monetary value, but also the people and places turned into commodities by trade and empire.
In short, this is definitely a mo' money, mo' problems kind of situation.
For Achille, the equation of love with silver coins devalues his relationship with Helen and his very life: "Wasn't love worth more/than the coins of light pouring from the galleon's doors?" (VIII.ii.45). Ultimately, he can't bring himself to take the galleon-coins, which represent for him "the ransom of centuries," a possibly unwholesome booty gained during an action for which "no coins were enough to repay its deep evil" (VIII.ii.46). He chooses to keep his hands clean of history's violence, even if it means not getting paid.
Coin are a mechanism for trade, too, which helps Walcott talk about the objectification of both humans and the natural world. As Achille witnesses the raid on his ancestors' settlement, he notes the inevitability of the future in the "tinkle from coins of the river, the tinkle of irons" (XXVIII.ii.146). The sounds of both river and leg chains echo the clinking of coins, grimly summing up the dehumanization of the slave trade, as well as the plunder of natural resources for money.
Here's a good rule of thumb for coins in this book: They highlight the problems that crop up when something truly precious is thought of in purely monetary terms. Along this line, Achille runs up against the juggernaut of the commercial fishing industry and its infinite appetite for natural resources:
[…] New silver was
the catch threshing the cavernous hold till each mound
was a pyramid; banks robbed by thirty-mile seines,
their refrigerated scales packed as tightly as coins,
and no more lobsters on the seabed. (LX.i.300)
The silver of the coveted fish is mirrored in the silver coins they win at market—and the silver coins that Achille will not see in his pocket at the end of the day because the seas have been fished clean. As in the other uses of the coin image, there is robbery here: of resources, life, and dignity. In the end, when silver mackerel once again grace Achille's nets, their sound is not the sound of fish flopping about in the nets; it's the sound of coins in a bowl (LXIV.iii.324).