You wouldn't think anyone would bother to make fake COACH bags because the originals are relatively inexpensive - at least compared to other high-fashion bags such as Prada, LV, etc. But as you know, people will do anything to make a quick buck. Fake COACH bags are a little difficult to spot, but here are some tips based on my personal experiences and observations:
Please note: I am not affiliated with Coach - I just love their products and hate to see people get taken advantage of...
1. Signature fabric: The "C" pattern will be crooked. Except for some newer patterns, like the "optic" or my new favorite "scarf print," the tip of the horizontal "C" facing the other "C" should touch. Also, the pattern should line up and start in the center of the front panel of the bag (same with the back panel). The center seam should go straight down through the middle of the CC's, and the pattern should be aligned horizontally and vertically. Also, the pattern should line up on any front or back pockets, so that it looks like there is no break in the pattern. (Note: Sometimes the pattern does not line up on side seams as this is nearly impossible to do.) The best way to tell is to go to the COACH website and look at the real thing, and then compare it to what you're looking at on eBay and see if the pattern is different.
2. Sometimes the "CC" will actually be a "GG" - how much more obvious can you get! And no, this does not mean it's a Gucci! (I'm not as familiar with Gucci products, but if someone is selling you a "COACH" bag which is imprinted with the letter "G" then logically it must be fake.)
3. The stitching or general construction of the bag looks sloppy - this is a sure sign because COACH does not make sloppy products! Each stitch should be the same length as every other stitch, it should be in a straight line, and there should be no "over-stitching".
4. The bag does not look like any other bag you've ever seen - if it looks "sort of" like a bag you've seen but something is "off" - be careful!
5. Replicas: The seller is listing an unusually large number of the same exact bag. This is a red flag because there are websites where you can purchase good-quality replicas, and I have seen these replicas listed on eBay claiming to be authentic. Note that replicas are usually made of fabric, as leather is more expensive and therefore all-leather bags are less likely to be fake. (However, I have seen fake Coach bags made of all-leather. The all-leather fakes are usually very easy to spot - i.e. the quality of the leather is VERY poor, the fixtures are all wrong, etc.)
6. Photos: Beware of blurry photos or stock photos (a stock photo is one that has been cut-and-pasted from the COACH website, usually with a white background) - this does not necessarily mean the bag is fake, but if you see either of these types of photos, I would contact the seller and ask if they can send you a photo of the actual item they're selling.