"No small part of the $1,000,000,000 which the Post Office Department estimates is collected annually in mail frauds changes ownership in what is known as the Spanish prisoner game-since the outbreak of the Spanish Civil War, the Mexican prisoner game. Ostensibly written by a person unjustly incarcerated in a foreign country, the Spanish prisoner letter enjoins absolute secrecy and asks for a sum of money to be sent to a friend to assist in obtaining the release of a sizable fortune in the United States. Despite innumerable official warnings, this old one still is being worked profitably. In March 1939, the Department of State announce the old hoax's most recent appearance as a form letter from Mexico offering a one-third interest for assistance in recovering $285,000 in a trunk in an unspecified custom house somewhere in the United States. In 1947 and 1953 a new wave was reported by the Post Office Department."For those with an e-mail account, this story will be familiar because this hoax/scam has now been renamed into the 419 or nigerian scam and you have probably received an e-mail that fits the description above.
It is interesting and exasperating that people are so gullible that a single scam can be perpetrated repeatedly for at least 60 years and people will still fall for it.
Update
While browsing the Quatloos website, I found out that the name of Senator Loi Ejercito had been used in a variation of this scam.