The fabric tag with the number and the microchip is supposed to be stitched into the seam in the zipped pocket. But your bag shouldn't have one - those tags were added either in 2015 or 2016.
As for what to look for to determine authenticity - usually, fake PS bags are of substandard quality, they don't use the correct fonts, the metal parts look cheap, etc. If you've seen enough of the real deal, you'll be able to spot those fakes. But then there are some "replicas" that are really difficult to catch, you have to look at every little detail.
Congrats on adding this beauty to your collection.