In the summer of 1919, Ponzi decided to set up a small office at 27 School Street, Boston, coming up with ideas and writing to people he knew in Europe trying to sell them as opportunities. A few weeks later, he received a letter from a company in Spain asking about the advertising catalog. Inside the envelope was an international reply coupon (IRC), something which he had never seen before. He asked about the IRC and found a weakness in the system which would, in theory, allow him to make money.