What is considered currency in Islam? Can gold coins, foodstuffs be used as currency? And are these modern bank issued paper notes shariah compliant currency?
According to Fiqh, it is not feasible to consider everything as money, haply nature circumstances of the money, (i.e.) feasibility of the usage of that as the instrument of value measurement could be considered as the indication of the nature of money.
Totally, money could be considered as all general instruments which are related to the measurement of the goods (with different values), such as metallic, papery and so forth.
Or for instance in Surah Toba:103, Allah tells the prophet that:
O , (you), the prophet, get Zakat from their property.
So the word (property) is related to the words cow, sheep, wheat, Sha’ir, Derachma (درهم), Dinar, date, raisin, and other things like them. Actually money could be related to whatever that could be named as an instrument to sell or buy the goods. therefore your examples could be true that gold coins , foodstuffs be used as currency. And likewise these modern bank issued paper notes shariah compliant currency.