Do you have any actual clear cut evidence from Qur'an (God) or authentic prophetic quotes(Prophet pbuh) forcing types of currencies? And please read what i said and don't bring me anything that talks about a currency as evidence of forcing it as the only viable currency. for example there are hadiths about riba(usury) talking about gold, silver, rice but it doesn't say these are the only viable currencies or necessarily their types just that you don't loan someone a certain amount of rice or whatever then ask for more(interest) of the same type of currency/commodity later. Also please when you try to search up something focus on God's words and his messenger not other people (you can think for yourself i believe in you)