Looks to be striation marks on the coin. I have a 2000 Jefferson nickel with them on it. Not 100% sure I think it is from the planchet. I looked at my coin and it is only on the observers too. I now think it is the Die something, cleaning or another happened.
They are rolling lines from the rolling out of the stock material. This is a real coin. When the BU look goes away, these lines appear. They are also temporary as they also wear off the tops of the devices. No premium for this. Just a spender. (keep the best, spend the rest)