There is an organization that specializes in old and rare coin dealing, called the Professional Numismatists Guild, or PNG. The group was founded in 1955.
Like many organizations, the PNG follows a strict code of ethics. In order to become a member of the PNG, an applicant must have a net worth of at least $250,000 at all times, abide by the PNG Code of Ethics and be at least 21 years old.
The code of ethics states that it against policy to misrepresent prices, and a PNG member is expected to always offer sound advice while educating those who seek its services.