Well, in DnD they have equipment lists with recommended prices like a sword for $100 gps and a mug of ale for 2cps and various prices in between. For the simplicity of calculation the exchange rate is generally perceived as 100copper pieces(cps)=10silver pieces(sps)=1gold piece(gp). In real life if 1oz coins were used the actual exchange rate would be 5625cp=54sp=1gp appx varies daily. In order to make the pieces appropriately sized to match the DnD exchange rate you could use 100 6oz cps=10 1/2oz sps=1 1/10oz gps.