Well there is no reference for these. They are just a mint error. They will look like this if they are legit:
1. Note how the weight on these will be the same as a cent 3.11 grams. 2. The thickness will be the same as a cent.
3. The devices will fall over the edges and the rim will not be complete on these coins. If the weight is 5 grams, and it is the same thickness as a nickel and the devices and rim are all present on the coin, then you have a nickel that was found outdoors that is discolored from being homeless for a time: