Purchased Michael Kors New with Tag to Resell

[captn-krunch]

I recently purchased a Micahel Kors Purse New with Tag but not from a store, I thought I was getting a good deal and could resell it.

Once I received the purse something told me there was something wrong so I looked the same model up on line and there are little things like 

the feet don't have michael kors printed in the metal, the one online does. The stitching isn't double, the one online is.

You get the idea, how do I find out for certain ?