I'm not an official authenticator, but I'm not on the fence about this bag. It's fake. This appears to be a knockoff Sam with tab. First, the leather should be boarskin (highly textured) and not smooth. Next, the embossed logo should be in gold and should be much higher, not 1/4 of the way down the bag. Next, (and the KEY clue) there appears to be a sewn-on tab inside. That tab should never be sewn to the bag as part of the zipper seam; it should have 4 rounded corners and be embossed with the kate spade logo (in gold) and perhaps have the country of origin (Made in Italy, Made in China). And it would be sewn all the way around just under the zipper opening.
I'd bet my Hagen-Daz on this being fake, but I'm sure the official authenticators will weigh in as well.