It has taken some time, but we can finally prove that there was duplication among the thousands (and perhaps tens of thousands) of Dear Doctor cards sent out in each mailing by Abbott Labs. A rather mundane hoard of cards sent to one doctor, William F. Henken of Racine, Wisconsin, yielded an interesting find. Among the 30 or so cards were a handful of duplicates.

Above are two card types as examples. The first was mailed from Catagena, Colombia depicting the San Felipe de Barajas castle. This card is known to have been posted over several weeks, and examples from August 16 and September 11, 1956 are seen here.

In fact, Dr. Henken's name must have been listed at least 3 times, because three Pedro IV Lisbon, Portugal cards were mailed to him. This card is known to have been mailed on only one day, November 26, 1956, and all three cards received the same postmark.

Remember that the late 1950's and 1960s were a time before computers and spreadsheets, so many of us collectors have always thought that duplicates were possible, but none have ever been reported before now. What is still not known is how doctor names were collected and added to the mailing list, and over what time period. Was a de-duping process ever used to remove possible duplicates?