I don't imagine JSA or PSA get the Marichals of the world wrong enough to even consider. However, with living guys like that, if you want certain authenticity and don't have the opportunity to get them in person, you might want to watch for private/public signings. There are several groups out there who are very trustworthy who hold signings and put their own hologram on the ball: MAB, Steiner, TriStar. Upper Deck is long gone, but their stuff is geniune. And, of course, you can't go wrong with an MLB hologram on an auto.
I'm sure most of us watch ebay AND every major auction we can find. However, if you've been reading the recent posts here, you'll see that none are immune from errors. (Check out the "Cuban Connection III" post: Jim Stinson made the best 1-line post I've ever read with regards to the Jose Mendez ball!) I'd suggest going slow on the biggies; unless you have a boatload of money and/or obsessive disorders combined with a need for speed, you can accumulate under-$100 balls for quite some time while watching, learning, and pricing the higher items. This very forum is a great place to learn, so welcome!!
There are also some very trustworthy dealers out there for older items, too. Nobody can ever be 100% sure about the Babe Ruths of the hobby, but there are people out there whose knowledge will get you closer to that 100% than JSA or PSA (in my opinion.) This is a good time to repeat Stinson's mantra: Ask every collector you feel comfortable with to name their top 5 dealers. You'll see a pattern, and that pattern is there for a reason. Of course, what Jim is too modest to say is he's going to be in pretty much every one of those top-5's.
Happy collecting!
Ken
earlywynnfan5@hotmail.com