The Gold exchange standard was similar to the Classical gold standard as it was self equilibrating in nature. Still, it had flaws, but one of the worst was the instability resulting from unexpected redemptions of gold. Suppose France had a trade surplus with England, France would receive sterling.
Before Money was introduced into human culture, the only way to trade goods was through bartering. Barter system relies on the principle of coincidence of wants; you hope that you will find someone that you need and who wants something that you have at the same place and at the same time.