Conservation

Hello all.
I have just purchased a lovely Demetrius I Tetradrachm. Whilst the reverse is perfect the obverse has some annoying black marks near the nose. Does anyone think ngc coin conservation service would be able to help make it look better
Thanks

 

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Without seeing the reverse?
I would leave it alone.

 

Looks alright to me.

 

If you leave it in that holder, check it frequently as I am almost positive it has PVC in it.

 

I expect they can remove the black stuff.

Silver is fairly easy to safely clean if it is high purity.

 

I'm not sure that the dark spots are PVC. It's difficult to determine based on the image. PVC deposits are dark green, and depending on how long the deposit has been around, the spot can range from hard to oily.

In any event, PVC can be removed with a 100% acetone bath. The acetone must be 100%, not the diluted perfumed nail polish remover commonly available in the beauty isle. The acetone will dissolve the PVC without harming the surface of the coin. There is a chance that the surface under the PVC might be different from the surrounding surface, but it should tone over time to a more uniform shade.

Using 100% acetone does require cautionary measures. The area must be well ventilated, don't breath the fumes! Also, acetone at this level is extremely flammable, so no open flame other source of possible ignition.

Depending on the hardness of the deposits, the coin might need to stay in the bath for, say, 10 minutes. Inspect the coin and put it back in the bath if needed. Oily PVC deposits dissolve almost instantly in 100% acetone. Once the deposits are gone, rise the coin with distilled water and carefully pat dry in a soft towel. Don't rub - gently pat the coin. Then, let the coin air dry for several days. If there are any areas that appear light is shade after treatment, they often darken over several days. I keep the coins that have been cleaned out for weeks, sometimes months, to help them "readjust".

Now, having said all of this, the dark spots on the obverse could very well be silver oxide deposits, quite minor as these thing go. They seem to be black. Acetone will have no effect on them. I suggest, then, leaving the coin alone. Any attempt to remove these spots chemically will very likely result in the loss or disruption of the really nice toning that the coin currently has.

That's a lovely example. Congratulations!