第一次世界大战期间,英国情报机关截获了一封奇怪的信件,发现这封信里只有一张贴着两枚邮票的白纸,一枚是面额二角五分的英国邮票,一枚是面额一角的法国邮票,情报人员对此迷惑不解。当反间谍人员用一张与信纸同样大小的透明欧洲地图覆盖在那张白纸上时,才恍然大悟。原来,当时正有二万五千英 During the First World War, the British intelligence intercepted a strange letter and found that there was only one piece of white paper with two stamps attached to it. The other was a British five-cent stamp with a denomination of one denomination French stamps, the intelligence personnel puzzled. When anti-spy officers with a transparent letterheads of the same size on the map of Europe covered in white paper when it suddenly realized. It turned out that there were twenty-five thousand British