We have 33 guests and 2 members online
At least, most sellers declare that they are selling copies. It's very important to read the whole auction description.
Watch out for the following words:
Another hint: Some sellers list every single item separately which is included in the auction and they use the word Original for them. But on the one or other item they don't write Original. Here you can suppose that these items are copies. So, you better ask the seller about it.
Here is an example (short version):
«Complete with original packaging box [...], foam tray is brand new and original,
plastic bag is brand new and original [...], Batteries included»
==> Read the full auction (PDF)
Next, you should check out the pictures very closely and recheck with the information here on the page Which Game&Watch items are copied?. Be very careful if the auction pictures are of poor quality. In this case it's very difficult or even impossible to detect copies.
If you are unsure, ask the seller and request more (good!) pictures. If he doesn't answer, then maybe better don't buy. Sellers who are too lazy to answer or who don't like critical questions should be avoided.
On the page Auctions with copied G&W items you'll see a list of live auctions where copied items are offered. Unfortunately it's impossible to track all these auctions all the time, but most of them are listed there.