That helped him persuade American investors in 1920 that he could deliver returns of 50% in just 45 days by exploiting a loophole in the pricing of international postal coupons.

• 这使得他在1920年说服美国投资人，他能利用国际邮政回答赠券定价上的漏洞，在45天里给予投资人50%25的回报。