How did professional coin dealers organize during the 20th century?

During the 20th century, the community of professional numismatists—or coin dealers—became increasingly organized as the hobby of coin collecting expanded significantly.1

As the market for coins grew and became more popular, professional dealers developed a more tightly knit community. To formalize their operations and professional standards, they established various trade associations. This professionalization occurred alongside the broader growth of the numismatic fraternity, which was supported by the emergence of coin shows, numismatic conventions, international conferences, and academic symposia. These venues provided the infrastructure necessary for dealers to interact, trade, and organize effectively within the hobby.12