How to Tell a Gold Coin?

We do not buy anything larger than a five gram bar over the counter. Large china is making counterfeits of all the larger bars. A heavy, heavy, heavy gold plate sotat the machine wol testit is fake. We have to cut the bar in half. Thats no le by ten real. So they're flooded and marten by the 18 thousand dollar machine that takes to tell themye. I've been gradually working on ancumulating what it takes to demonstrate roman debasement through the later empire.