Green Spot On A Coin Inside A PCGS/Ngc Slab

I actually have several modern commemorative dollars with 69 PCGS/NGC grades that have small green spots.

I'm assuming since it is green it's some type of corrosion.

I also assume it wasn't visible when the coin received a 69 grade. I'm not sure how much magnification the graders use.

I'm not the original owner of the slab but the coins are currently in a climate controlled environment.

@SsuperDdave:

I would lean more toward it being Verdigris since they are modern commemorative dollars. So is it best to break the coin out of the holder and dip it in something like eZest? I've done that before with silver coins and it removes the green but leaves a dark spot. Is there a better way?

Would they still grade 69 with a Verdigris Spot or has that developed after it was graded in the slab? How might that happen after the fact?

The slab wont prevent anything already on the coin from continuing to react with it. Kind of the same way milk spots can develop after slabbing.

For 69s youre best bet is probably to sell them and get new ones. Youll probably lose a few bucks on each but that difference wont be as great as the cost of regrading them if thats what your intentions were.

IN this case wouldn't the TPG concerned buy the coin back?......they should have picked up the problem ( or its precursor) at grading

I can't tell much, can you get a close-up of the spot? It looks like plain old verdigris. Make sure you store it inside a ziplock with desiccant and it should be fine. The most common mistake people make with slabs is thinking they are fully protected and safe....not true. Slabs need to cared for just as a raw coin in a 2x2.

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