The biggest one is the creed patch. The lettering should be well spaced and there should be no misspellings in it. Here is a clear example of a bag that is counterfeit, the word "enduring" is misspelled and the style number, when you research it shows a completely different bag. This happens to be a very commonly counterfeit style number.
This is the bag the creed patch above is from
And this is the bag for that style number
So, if the creed patch appears fine, next, take the style name and number and do a search on google. Go to "images" and there you should see pictures of your bag. Now, the lack of pictures does not automatically mean your bag is a fake, so take a deep breath. Many of the bags we sell are no longer in production and people may not be willing to part with them, so you won't see them for sale. I would say that 98% of the time you will see at least a couple of bags that will match so, while it's not foolproof, it's a good first step and may be all you need.
NOT ALL COACH BAGS HAVE CREED PATCHES!!!!
A very common misconception is that if it doesn't have a creed patch, it's not authentic. WRONG, WRONG, WRONG. Typically Coach does not put a creed patch in wristlets, wallets, swingpacks and other accessory type bags like the top handled pouch bags. Occasionally they will have one if they are a limited edition or otherwise special production, but it's quite common to see them without. Your larger bags that are termed "handbags" according to Coach will always have a creed patch.
Here we searched for the COACH Poppy Storypatch Shoulder Bag 44088
As you can see, there are plenty of these bags available to verify that your bag is authentic. Don't worry about the bags that don't match, sometimes people get the names or numbers wrong, or if there are no other bags that match the search query you'll get the next thing on the list.
You probably won't question a bag that has the sales tag still attached, but in case you do, here is the tag for the Poppy bag above. It's true that tags are not necessarily proof, as sales tags can be counterfeit as well. Usually they lack some of the information that an authentic tag will have. It will have the style number and it will have an abbreviation of the style name. Here is an example of the Poppy Story Patch. You can see the abbreviation for the bag Poppy Story Patch Top Handled Bag and the style number 44088 and the color is the Blue. It matches the bag you have and the bag in the search.
There is a misconception that the pattern must match at the seams. This is not true, what is true is that the pattern will always be centered. It's almost impossible on some patterns to match it exactly, but as you can see here the pattern is not centered at all.
Here you can compare, notice the symmetry
In addition to symmetry, Coach always has the signature c's in pairs, never in single rows:
YKK zippers are not always used on Coach bags, despite the fact that many so called experts will tell you this.
You have to be very careful using random websites out there to get your information. Many of them have false information. There are only 2 places I trust to get my bags authenticated for free, and that is The Purse Forum Those gals know their stuff. The second place is ebay's community forums in the Clothing, Shoes and Accessories Forum
The best thing to do if you question the authenticity of your bag is to talk with your seller. Most times they can calm your fears and reassure you as to the bag's authenticity.
We, at The All Coach Partner Auction do purchase directly from Coach, but much of the variety that we are known for comes from other resources. We spend a lot of time authenticating our bags for you. We don't bring you the bags until we are certain they are authentic. Our reputation is important to us, and you, our customers are important to us.