2021 25c Proof Crossing The Delaware-What Are These Blue Streaks On Obv?

I opened the case and found that the blue streaks were on the coin, not on the case. I used a soft cloth to see if the streaks would wipe clean, and they did! Could be something used at the mint to polish proof coins which left a residue?

Will do, John. I'll post pics later this afternoon.

Here are photos of the coin after it was taken out of the holder, and lightly cleaned with a soft cloth to remove the blue residue. Should I soak the coin in acetone to more fully clean the coin?

Thanks for your response, NumisEd. Since I took it out of the holder and gently wiped off the debris, I didn't know whether it would be best to give it the acetone soak for conservation before returning it to the holder, or just leave it as is.

Acetone cannot hurt your coin. If this was some sort of contaminant, it might be a good idea to use the acetone on it. But its your decision.

As to using the cloth, try forced air next time a situation like this comes up. Even something as simple as an eye dropper can work for some things.

I would definitely give it an acetone treatment. Some of the containment could remain. If it was grease, a remaining thin layer may have been what prevented the cloth from scratching the surface.

Remember, any acetone soak is followed by a flowing rinse with fresh acetone (not the batch you used for the soak). Do not rinse with water! Do not wipe dry! Fresh acetone should air dry faster than you can whip out a cloth to wipe it!

Sounds good!

You are welcome.