with ANY dealer that uses NO third party authentication, PARTICULARLY for high end items. Not that every item they offer needs to have PSA or JSA but that the dealer employs a standard. Although authentication services are not perfect, they are a skilled second opinion AND an opinion that is independent and has NO financial interest or bias as does the dealer selling the item. Also, think twice about any dealer that is against third party authenticators as it may signal they have something to hide.
2). Dealers who provide poor images or NO close-ups of the signature on their web site, so you cannot easily examine the autograph. They may have a reason why they do not want you to see close-ups. For example, dealers selling “clipped” signatures of high end items like Ben Franklin for $15,000 and not even post a close up image of it on their web site. AND, no third party authentication. Some of these dealers are relying on the inexperienced, vulnerable buyer (i.e. victim) to come along.
2). Never buy “clipped” signatures of high value autographs like Abraham Lincoln as MANY (if not most) are forgeries. Only invest in official documents like Presidential Appointments. Forgers are not likely to spend hundreds or thousands of dollars on an Abraham Lincoln document just to forge it (have never heard of such a case in 30 years of collecting).
3). Be very cautious of Group photographs like complete TV show autographs or autographed movie posters by cast members (i.e. Rat Pack), as many (if not most) are secretarial or outright forgery. It is very difficult to get an entire cast to sign a movie poster. And, as for vintage movie posters (prior to 1975) I don’t think I have ever seen an authentic one that included major stars. I noticed a web site that sells autographed movie posters like the Godfather, including Marlon Brando’s signature. They are all forgeries. A genuine Godfather autographed poster, with Marlon Brando, has NEVER appeared on the market.
4). Since we cannot get in person autographs from deceased celebrities we must rely on signature studies and recognized reputable authentication services like PSA or JSA (although they are not perfect, since they are humans, they are by FAR the best in the industry). I have tracked ALL of the authentication services and forensic “experts” for many years, so I am speaking from a lot of experience. Yes, I am a bit of a nerd with autograph authentication, since it is the foundation of the entire autograph memorabilia industry. And, there is a reason WHY most major auctions and dealers selling high end autographed memorabilia use either JSA or PSA, above all the other services out there. Yes, you will read online from a minority who don't "like" PSA or JSA. But are these reputable sources? Are they major auction houses or reputable dealers?
5). Many dealers are NOT collectors. They will sell anything, including autographs they have NO knowledge on or experience with.