Be very cautious of purchasing from Hong Kong.
We recently purchased one from there and it was a fake.
Ask for pictures of the item to be purchased. Compare these pictures to what i say below. Dont bid in private auctions you will end up paying more for a fake at worst.
Things to look for are :
Sink marks in the plastic, these occur when insufficient plastic is pushed into the mould. When the plastic solidifies it retreats from areas such as internal ribs. Like areas around the screens and buttons.
The hologram if fitted. Box should have nintendo stamp.
The quality of the box is completely different. A real one is more akin to a mobile phone box with a plastic type feel, not just cardboard.
Typing errors in the instruction manual. And it looks basic.
Insufficient paperwork included. You should typically have :
Nintendo club leaflet, Instruction Leaflet, Accessories Booklet, Health and safety Advice.
Spare stylus is usually missing.
Incorrect power adaptor. Probably the most telling item. Ask to see a picture of this as it should be a genuine Nintendo item made for this product item complete with Nintendo stamps.
If you have bought one :
Check all operations work. Common defect is the touch writing surface not recognizing certain areas. Faulty ones are being advertised on Ebay with this defect.