I found this in yahoo answers.

Coach Bag Serial Numbers Lookup Tool

Can You Look Up Coach Bag Serial Number

This bag with the leather stamp inside but no creed is actually the same style of bag as the black bag above from New York City. This bag was made prior to the time when Coach adopted a creed, and prior to the time when they had serial numbers inside the bags, yet after the Coach metal tag from below, placing it late 1960's, early 1970's. A correct serial or style number will never prove that a Coach is genuine, but an INCORRECT number will almost always prove that a bag is fake. The authenticators can list every single reason your bag is a fake & you still won’t believe it. You trust a consignment shop that most likely has no experience authenticating vintage coach bags over. The serial number is at the bottom of the tag and contains a minimum of 4 letters and 4 numbers. Call Coach customer service at 1 (904) 741-3090 and give the representative your serial number. All authentic Coach bags are registered with the company in their database and the rep will be able to verify the bag’s authenticity. Coach Bag Serial Number Search The bucket bag has become the key shape to be seen with and is loved for its roominess as well as its chic style. Vera Pelle bucket bags will provide a touch of Italian elegance and can be bought in stylish two tone leather colours, or in plain leather, including bright red, fuchsia pink or black.

Coach Bag Serial Number Lookup

The following numbers will always indicate a counterfeit Coach bag, especially any serial number starting with NT- or TN- :
NT-4903 NT-4908 NT-4115 NT-4157
TN-9085 TN-9096 TN-9951 TN-4186
7H-7456 4C-9911 40-8624
In fact, ANY Coach bag with only two letters or one number and one letter to the left of the hyphen can be assumed to be fake, whether or not the number is in the above list
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These are just SOME of the numbers found on counterfeit bags that were made In Korea:
501-02 701-02 101-22 101-147 and anything starting with 101-,102-, 201-, 202-, 301-, etc.
but there are many more number combinations being used. Coach bags will never have serial numbers in these formats, and will NEVER say Made In Korea. Coach has never made bags in Korea.
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Almost all numbers beginning with H4B- are fake, like these:
H4B-0532 H4B-0516 H4B-0678 H4B-0517
except for H4B-8983 which should only be on a Scooter Bag and H4B-9948 on a Bucket Bag.
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More fake numbers:
M4N-4154 012-3445 308-9937 308-9875 - this one is VERY common
J4D-4133 is fake unless it's on one of the classic Waverly Totes.
Always check a bag's serial number and be sure the style number actually belongs to that bag. It still may be counterfeit, though, so don't use serial numbers as your only test. The counterfeiters also use many legitimate-looking serial numbers but on the wrong style bags or accessories, like -5659 which should only be on a Scribble Tote, -6094 which belongs only on a Signature Demi, -9956 from an all-leather Pelham Bag, and -1417 which should only be on an East-West Leather duffle. Accessories with style #5077 are fake, that number belongs to an Optic Bee Tote.
Fake pebbled or nubuc leather Sonomas are showing up with incorrect numbers - Sonoma bags from the mid-90s should always have style numbers starting with 49xx except for about half a dozen exceptions.
Many popular bags from 2006 and 2007 are now being faked and have serial numbers starting with 'M3U-'. These are all fake since a Coach with that year code would have been made in 2003.
A correct serial or style number will never prove that a Coach is genuine, but an INCORRECT number will always prove that a bag is fake.
Step1
Look at the pattern on the outside of the bag. Most Coach bags have a 'C' pattern. On a true Coach bag, this pattern will start in the middle and extend outward. Also, an authentic Coach bag will have the tip of the C touching the tip of the opposite C.
Step2
Look at the seams. In a real Coach bag, the middle seam will go straight through the middle of the Cs, and the C's will extend to the sides of the bag. If the Cs are cut off on the sides, it is probably a fake bag. The stitching should also be very neat and well done, with no overlaps or dangling thread.
Step3
Look at the logo carefully. One very obvious sign of some impostor bags is that instead of a 'CC' logo, it looks more like 'GG'.
Step4
Check out the style of the handbag. Does it look like something Coach has released recently? Before you buy a Coach bag off the street, on eBay or at that swap meet, take a look around a high-end retailer to become familiar with the styles of real Coach bags.
Step5
Open the bag and look inside. Is the Coach logo repeated on the lining? If so, repeat the previous steps for checking the logo and stiching. Look for a serial number because on the larger Coach bags, there should be a serial number stamped on a square patch of leather sewn into the lining.
Step6
Examine the hardware. Coach uses only the best. Is the zipper of high quality? Coach bags have 'YKK' stamped on their zippers. Also check out the tag; if it says, 'Made in China,' it still might be a real Coach bag, but it is definitely a fake if it says, 'Made in Korea.'