Rust spot or chocolate milk spot?

[capegreg]

Why does this look like a rust spot? Counterfeit perhaps?

 

[Just Bob]

It can't be rust, since the coin is silver, but it can be a toning (tarnish) spot from some foreign substance that was on the surface of the coin when it was encapsulated. It could have been something as simple as someone sneezing near it.

[Numismatic, A.A.S.]

Just Bob's post is right...remember these have delicate surfaces...just like some of the Spouse Gold Coins with red and black specks developing...

[coinman1794]

It's possible this could be a toning spot or a dip spot. However, Silver Eagles have been plagued by tiny round strike-through errors, typically from blobs of congealed die grease dropping onto the coins during striking. Most of the time, the grease falls out, leaving a cavity; but sometimes the grease blob is retained and looks very much like that spot. Because these are Mint Errors, they do not affect the grade, in most cases. However, when you are distinguishing between 69 and 70, they very well might have an effect. Spot or strike-through, I would have that coin reviewed.

[numisport]

Oh yes appearance review is no charge (besides shipping) and they might replace it. But be advised you might get that coin back in a 67 or 68 holder with a FMV adjustment. Does it make you wonder how this could grade 70 with stuff on or struck into the surface ? Never mind the technical nuance of what graders think a 70 should be; to me it has to look flawless in hand.