Labels. Few designers use hanging tags on their items. None of the high-end ones do. They also rarely sew labels inside or out. There will be a logo somewhere that will identify the bag to those in the know. The big name tag on the outside is reserved for cheap tee shirts and the rear pocket of off-the-rack jeans.
Linings. Know what your chosen designer uses to line bags. If it’s a signature logo fabric, know what it looks and feels like. If it’s leather, know what kind. Color is vitally important as a clue.
Dust bags. Don’t be impressed because your eBay “find” has a labeled dust bag. Anyone can make one of those. It means nothing. Some designers do use them, though, so find out about the one you’ve chosen.
Logos. Where does the logo appear and in what form? Louis Vuitton is very specific about logo placement. The LV imprint in the leather pattern has to appear in specific locations and a set number of times. There will, for instance, be three LV’s on the front of a bag, period. They’ll be right-side-up on the front. They will never, according to the Louis Vuitton expert, be outside the feet on the bottom of the footed bags. Details like this may seem insignificant, but they scream “fake” to anyone who knows the real deal.
Serial numbers and other stamps. Louis bags are stamped with the date of manufacture. The stamp appears in a specific spot and only in that spot. Naturally, even the fakes are stamped now, but not in the right place. “Made in __” stamps mean nothing and generally signal a fake. Be particularly wary of designer bags with “Made in China” stamped or tagged inside. There are no European or American designers producing bags in China, Taiwan, Japan or Thailand. Designers do not need cheap labor. They charge as much for their bags as some families pay for six months’ groceries!
Beyond these basics, things get very complex. The dimensions of the leather trim on the bag, the size of the stitching and color of the thread, the type of metal used in rivets and studs . . . all play a part and all are very specific to the individual designer.