@givemersspls
You do not submit control of the currency to someone else when you are the local power.
And goverments hold a monopoly over the currency of their nations, no one else is allowed to make more, try and duplicate a dollar and youll be in federal jail faster than you can say "didnt know she was 12".
Germany, has absolute control over how many Euros are printed, let that sink in.
And my example of the Peso is completely valid, and here is why.
if the US adopted the Peso, then they would be beholded to how many pesos they receive from the mexican goverment and the mexican economy.
It would skyrocket the price of the Peso agaisnt the dollar in the free market exchange, since the US adopting the peso means that the USD no longer holds the same value. Thats why many countries have USDs in their coffers as backing for their own currency.
In the story, the dude can produce anything he wants, at this point the medals are no longer being valued as individual goods, but as the MCs time.
If he adopted a foreign currency, then they would set the prices for the goods, not the otherway around.
Lets use real world comparison for something the MC made.
A barrel of wine costs around 400 USD, for an american oak barrel.
900 USD for French oak.
A 20 dollar gold coin today costs 1200 USD.
If we do some minor converstions, with lots of leway, a barrel of MCs wine could be worth around half a gold coin. or 50 silver if we go by usual Isekai standards.
Now remember, he is the all powerful MC, theres nothing that can challenge him in terms of military might, why the hell would he allow his precious time to be set by another nation?
It would be stupid.