As seen in both the first John Wick movie and the subsequent sequel, it seems these gold coins are used as some sort of currency for the underworld of hitmen and other nefarious figures.
That said, it's not made clear what the value of the coins are, or what services can exactly be bought with said coins. From what we've seen, the currency has been used quite a bit:
- John's used it to pay off the bodybagging crew after the home invasion
- He's used it to procure information on some other people
- He's used it to gain access to hitman-tailored shops
- Cassian's used it to buy drinks for him and John
- John's used it in order to get in contact with the Bowery King
And many more scenarios, but is that really all the currency is used for? Could the currency be used outside of that underworld? And besides all that, the actual value of it seems quite odd. Cassian spends 1 gold coin paying for his and John's drink in Chapter 2, but it seems that the same amount can be used to gain access to specific hitman services, but it costs a whole lot more just to get a cleanup crew to dispose of the bodies.
If anything, is there a set value of what the currency can be used for? Can it be used for anything, or are there some restrictions on how it can be used.