I didn't notice this till I listed it on eBay and it got more attention then a circulated nickel should get. I really can't figure it out more then just a shadow effect and trick of the eye. No reason for this to be here.
Too small to be a devices. Also they would be raised on the coin as tall as the mintmark is raised. If they were devices, then where are the rest of the devices that should be there if this were a die issue? It is not.