You may not always be right, but you are less likely to be sorry. Although some persons who establish and operate dishonest firms change their own names as often as they change their firms' names, even the hint that you are the kind of investor who checks into things like that can be a fast turn-off for a swindler. And there can be requirements that you be provided with this information and acknowledge in writing that you have read and understood it. Obviously, it's not the sort of information a swindler is likely to distribute. Some bona fide investments are and some aren't, but fraudulent investments never are.
Exchanges have strict rules designed to assure fair dealing and competitive price determination.
There are also in-place mechanisms to provide for rule enforcement and to impose severe sanctions against those who fail to observe the rules. If the salesman rattles off a list that ranges from the FBI to the Boy Scouts, tell him you'd like to check the firm's good standing before making an important investment decision. Then verify the response. Few things discourage a swindler faster than the thought that his first visitor the next morning may be from a regulatory agency. At the very least, keep in mind that any ongoing supervision which isn't being provided by a regulatory organization or agency will have to be provided by you.