Producers bring useful commodities to the market which can be exchanged for other useful commodities. A gold mine brings its own unit (gold) to the market in exchange for other useful commodities.
A most universally exchangeable commodity arises and circulates as a currency; a most suitable currency arises as a money.
Money is a medium for transferring utility which can be used to represent a simple or complex underlying value (i.e. one or more commodities).
Money that has a value which well reflects that which it represents is honest or good money; money that does not well reflect that which it represents is considered of poor quality.
It is difficult (impossible perhaps!) to determine the specific underlying commodities (and their weights) a money represents, however, the markets CAN be used to determine a money’s quality (or “honesty” in this respect).