Odd blemish on Gold Proof Kennedy Half Dollar

[elvee426]

I recently purchased some coins privately and wanted to ask about one of them to see if anyone can shed light on a blemish.  The coin is a gold proof 50th anniversary Kennedy Half Dollar, and the blemish is obvious on the front, less so on the rear where it appears at about 4 o'clock on the edge.

My questions are:

1. Does anyone know what this is?

2. Can it be fixed (I assume not)

3. How would this effect the price? Link to Chards Listing (£1563 at time of posting)

Thank you for any information you can provide.

 

[Alex944]

This looks like some copper spotting to me, though the one on the obverse shows a blueish hue in the center and I have personally not seen that before. The spot on the reverse does look like a classic copper spot. This can happen (even on .9999 fine gold) due to residue on the dye/planchet during the minting process. It may not be visible for a period of time (can be months or years) but gradually develop.

There are some methods on removing these spots from a coin, but fair warning that this MAY (it doesn't have to) cause some minor damage to the coin, so I would strongly advise to do further research in how to remove them OR have it submitted for professional conservation since it's a proof. If this was just a bullion coin I wouldn't be too fussed about attempting the removal myself, but with a proof I wouldn't want to touch it.

This video from Backyard Bullion explains the above a bit more and shows the method of cleaning spots with tinfoil/bakingsoda and water: 

Best of luck, beautiful coin either way and interesting weight.

Alex

[ArgentSmith]

DO NOT attempt to clean with baking soda and tinfoil ffs 😂

[James32]

41 minutes ago, ArgentSmith said:

DO NOT attempt to clean with baking soda and tinfoil ffs 😂

You not like tinfoil?

[ArgentSmith]

 

1 hour ago, James32 said:

You not like tinfoil?

It was invented for making hats... not cleaning coins!

[elvee426]

3 hours ago, Alex944 said:

The spot on the reverse does look like a classic copper spot.

Thanks for the info!  I'll watch the video, but...

 

3 hours ago, ArgentSmith said:

DO NOT attempt to clean with baking soda and tinfoil

.. I won't attempt myself!  May look into having it done professionally, or just take the hit on the value.

[Petra]

Not something I would do, however I assume that there is a chemical reaction with the foil and baking soda. Whether this combination then reacts with copper?

not sure what if anything else you could practice on!

Best to leave it