Inside of your bag there should be a Gucci flap label, under that label are the serial numbers.
Flip it over and see if there are numbers.
My bag is all leather, has leather lining inside, the inside zipper is a Gucci GG pull.
If you have a fabric Gucci bag, it will have a fabric lining. If you got leather, it will have a leather lining.
And the flap inside with the name tag has numbers under it.
You can also, go to the Gucci Website directly and see if the bag you have is on the site.
http://www.gucci.com