Initial deliveries went to post offices on Monday, May 13. Aware of the potential for inverts, a number of collectors went to their local post offices to buy the new stamps and keep an eye out for errors. Collector William T. Robey was one of those; he had written to a friend on May 10 mentioning that "it would pay to be on the lookout for inverts". On May 14, Robey went to the post office to buy the new stamps, and as he wrote later, when the clerk brought out a sheet of inverts, "my heart stood still". He paid for the sheet, and asked to see more, but the remainder of the sheets were normal. The postal clerk who sold the sheet later said he did not realize the image was inverted because he had never seen an airplane before.