About the 24x36" Posters...
I have posted to this thread before...I am an avid "Think different" collector, I mainly collect the 24x36" size, and I am only lacking a few of them in the series...
But I must say -- they are more and more counterfeits appearing on eBay these days, and they are getting harder to decipher. Sellers with high feedback ratings are posting ads saying "Stored in tube since acquired, former Apple employee, unrolled only once to photograph, in mint condition, etc"
Some will even go to the extent to post photos of StartingLine official mailing tubes that the Think different sets were mailed in (in 1997-1998).
You really have to be careful, it is difficult to find genuine good posters these days.
I know for a fact that all of the posters offered from Germany (for the most part) from eBay sellers such as vitor-belfort, are reprints, and not originals. They are "good" reprints, the Buzz Aldrin posters he offers are very crisp, high quality posters, but not the original zoom-distance Buzz Photo that is featured on the -Authentic- poster from Apple, which shows a larger, closer-zoomed Buzz. The Albert Einstein posters from this seller are lower-quality, you cannot see the knit sweater stitches, which are all visible on authentic Albert Einstein 24x36 posters (and these are EXTREMELY hard to find)....
There is one seller who seems to be offering some authentic rarities such as a Dalai Lama for $599 (on mounting board), a Charlie Chaplin (sold) a Flick (Bug's Life) - for $1499, and a Francis Ford Copolla for $999...he has posted a long story on the listings of how he supposedly acquired all of these posters, and says they are 100% authentic -- his prices on them are astronomical and out of the range I would pay, considering that such paper-good posters can be easily reproduced, and these could easily be undeniably-authentic knock-offs that would never be proved otherwise, so no way am I shelling out that cash for those posters. I would be interested in a Dalai Lama, but the one he is offering is permanently affixed to styrofoam board (glued)...which detracts from the collectible value, in my opinion.
The highest valued easily-obtainable posters at the current moment are probably the Richard Feynman, the Ansel Adams, the Jackie Robinson, and the Frank Sinatra...
Amelia Earhart, Thomas Edison, Pablo Picasso, Alfred Hitchcock, Ghandi....are probably the easiest and cheapest ones to find...
Joan Baez, Jim Henson & Kermit, Miles Davis, Maria Callas, Lucy & Desi, Martha Graham, and Ted Turner are also easy-to-find but I see them in lower numbers than the previous ones above.
The "Director's Series" (featured in large banners at Macworld SF 2000) was the last series to-be-released, and was never released. "Supposedly" a few were printed and given to Apple employees and featured within the Apple campus, and these posters, the eBay seller claims he acquired in California and that they are originals, rare, and worth the money he is offering them for. So far, those posters have been up over 6 months and he has only sold one or two of them. Lately, I have seen a number of the Flick posters being offered (24x36") at much lower $75-100 prices, so I grabbed two of these, with the thought they "could be" originals and "may be" rare and worth something. Who knows, they may be reprints, I've never seen the original.
So, as for re-prints, you need to look closely at the printing....does the printing look "too dark" -- is the image "blurry" -- or does it seem pixellated, as if printed from a low-res JPEG image?? I once bought a Richard Feynman poster from eBay, and found it to be a fake re-print, because I knew what the original looked like....the one I had was grainy and pixellated on close inspection, and they guy had sold it to me for over $275 -- yeah, so you must be very, very careful in buying these expensive collectors Think different posters.
If you see somebody offer a listing of them, including 4 or 5 posters which make up one of the "official" sets, and the photos are actual pictures of the laid-out posters, taken by a reputable eBay member who says they have owned these posters, or bought the set years ago -- there is a good chance that this is the REAL DEAL and they are real posters.
If you see somebody offer a load of posters, mixed of different sets (usually from the German eBay sellers), who will start these auctions off cheap -- pretty much all of these German posters are re-prints, and not originals, maybe worth the $12 - $20 that you are willing to spend, but not worth anything more than $30.
Original 24x36" posters are a bargain at $50 or less, still reasonable at $75...the common ones I have seen go upward of the $100 - $135 range.
The rare ones, such as the Richard Feynman - a very "sought-after" poster, I have seen go for over $200.
In my opinion, the two rarest of the 24x36" -released- posters are the original Albert Einstein, and the original Buzz Aldrin, which are incredibly hard to find now. Again, the ones offered by the German sellers are re-prints, I have only seen originals on eBay 2-3 times in the last 12 years.
An original Albert Einstein 24x36" was offered by RedLightRunner a few year ago for $600, and it did sell. It is no longer offered. There was also one on Amazon's website, but it is no longer available. I have seen a pair of them on eBay a couple years ago, they were originals but had crease damage. The Einstein posters offered by the German sellers are re-prints, as I have said above.
I hope this short bit of my experiences in Think different poster collecting has helped you understand and be prepared in your buying and collecting adventures...just be smart, educate yourself, and know the market. If you have a gut feeling that something is a knock-off poster or re-print, it probably is. Do not hesitate to message the sellers with as many questions to possibly verify authenticity, it is your good money, after all, and the way I see it, this is both a fun hobby and a smart investment for the future.
Good luck, happy collecting, and don't forget to "Think different"