Newbie Question - Black Spots on Quarters 0

[Seamus8]

I have been seeing a lot of quarters with a green to black gunky tar like substance on them. I now know that you are not supposed to clean coins. So, my question is there an approved safe method to remove the gunky substance without sacrificing the value of the coin? I am enclosing one example.

 

Edited December 24, 2022 by Seamus8

[Coinbuf]

You can soak it in acetone, that is completely safe and will not harm the metal.   May take some time to soften and loosen that heavy a build up, and you may not like the look of the coin once that is done if the gunk has started to eat into the metal.  Just curious why would you want to clean/save such a common coin in that condition?   It is clearly circulated and has no value over the face value.

[Seamus8]

I am not going to save the coin I used in my example. I just grabbed the first quarter I saw that was covered in gunk.

Just curious if you were to grade it, what number would you give it?

[Sandon]

   Without the "gunk" it would be an AU50 or so. With it it's "AU Details, environmental damage". Either way it's worth face value.

  Do you have a grading guide and other basic numismatic references?

[Seamus8]

I do not have a grading guide. Can you suggest where I can find a good grading guide on-line?

[Sandon]

   Please refer to the following topic for both printed and online resources that I regard as essential to success in becoming a knowledgeable collector:

  This topic includes a reference to PCGS Photograde, an online photographic grading guide. However, I strongly recommend that you obtain and study a printed grading guide that includes written descriptions of each grade for each series, such as the Official A.N.A. Grading Standards book referred to in the topic.

[Just Bob]

A light oil, such as mineral oil or olive oil, will sometimes loosen caked-on dirt and other gunk, but it takes a long soak. Sometimes several months of soaking is necessary to loosen stubborn material. Also, be aware that olive oil is slightly acidic, and long soaking may have an effect on the color of copper or copper-containing alloys, such as bronze or brass.

[EagleRJO]

On 12/23/2022 at 10:59 PM, Seamus8 said:

I do not have a grading guide. Can you suggest where I can find a good grading guide on-line?

This is a start, and then zero in from there using the ANA and PCG$ guidelines.

 

Edited December 24, 2022 by EagleRJO

[Seamus8]

Thank you. The chart you sent definitely helps a lot. But now I have two other questions that maybe you can answer.

After reviewing the chart you sent, can a coin found in circulation be graded as a mint state 60-70, depending on its wear?

I have a few coins that I have in my pocket change stash that look to me to be about a mint state 64 or 65. Can they be graded as mint state?

[EagleRJO]

On 12/24/2022 at 1:14 PM, Seamus8 said:

After reviewing the chart you sent, can a coin found in circulation be graded as a mint state 60-70, depending on its wear?

Yes, a coin actually in circulation can be graded mint state if there is no wear.

[Seamus8]

Thanks. That answers that question. As I am new to this hobby, I thought that was the case, but I figured I had better ask now rather than later.

[Sandon]

   

On 12/24/2022 at 1:26 PM, EagleRJO said:

Yes, a coin actually in circulation can be graded mint state if there is no wear.

   Bear in mind that "wear" may include the slightest amount of friction ("rub") on the highest surfaces of the coin. If you hold the coin at an angle under magnification, you can see the loss of luster resulting from the friction.  (The grading services tend to allow a small amount of "rub" for older coins and give the coin a lower mint state grade, but I've never agreed with this practice.)

[Coinbuf]

On 12/24/2022 at 11:14 AM, Seamus8 said:

Thank you. The chart you sent definitely helps a lot. But now I have two other questions that maybe you can answer.

After reviewing the chart you sent, can a coin found in circulation be graded as a mint state 60-70, depending on its wear?

I have a few coins that I have in my pocket change stash that look to me to be about a mint state 64 or 65. Can they be graded as mint state?

As someone that is new to the hobby do you think you can identify "wear" correctly?   I'm not asking that to be snarky but because it is a very valid question and a skill that many people new to the hobby cannot do although they often think they can.   As Eagle said it is possible even likely for very newly minted coins found in circulation to grade as uncirculated if they are pulled from circulation before those coins are slid across the counter too many times.   However, many coins that may look unc to someone new may have significant friction on the high points if viewed under a proper light source and angle.  I put together my state quarter collection completely from circulation, and many of those coins look like gem uncs, until tilted and viewed correctly to discover the rub.

Edited December 24, 2022 by Coinbuf

[EagleRJO]

On 12/24/2022 at 1:29 AM, Just Bob said:

A light oil, such as mineral oil or olive oil, will sometimes loosen caked-on dirt and other gunk, but it takes a long soak. Sometimes several months of soaking is necessary to loosen stubborn material. Also, be aware that olive oil is slightly acidic, and long soaking may have an effect on the color of copper or copper-containing alloys, such as bronze or brass.

And do NOT get impatient and try to use something, like a toothpick, to further loosen any gunk.  I already knew this but tried it with a garbage coin just to check out the results, and everything may look great until you get out the loupe to look at the coin.  Very clear scratches or scrape marks no matter how careful you think you are being!