This is hard to believe. 10 permute 5 is just over 30,000. Unless stamps were less than 3 cents, that scam wouldn't work. First class stamps have been 4 cents

This is hard to believe. 10 permute 5 is just over 30,000. Unless stamps were less than 3 cents, that scam wouldn't work. First class stamps have been 4 cents since 1958. Not to mention the labor of preparing 30,000 index cards. TL;DR Your dad should have gotten a job.