20 dollar St Gaudens (No grade from PGCS because of cleaning) Does not look like it was cleaned.

how can you tell if this was cleaned?

 

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Tilt the coin under a strong light and look for hairlines going in roughly the same direction. Based on this image, the problem area might be the obverse around the olive branch.

Or, it's possible PCGS made a mistake. It happens.

 

Luster is suboptimal, normally they tend to grade a point of two lower, when they detect market acceptable Cleaning.
Your coin is borderline, a light cleaning was done.

 

What I see (or actually don't see) is toning in the protected areas.
With gold that's not as definitive analysis as it would be with the other metals since gold doesn't tone as obviously.
The lack of toning points to dipping, not wiping.

 

I have read that the TPG's use "sniffers" that can detect if certain chemicals have been used to dip the coins, etc.

So as Kanga said, perhaps it was just lightly dipped. The other posters may be correct as well.

 

To me the coin's fields show no luster. Looks at the grainy appearance between the UNITED down to the eagle's head. Should be frosty, but there's no luster left. Sharp detail but no originality. Someone wiped it fairly harshly.

 

I think the best hint - not that anyone can tell for sure about cleaning from one set of small images - is to be found at the bottom of the reverse on the sun.

 

The "sniffer" cannot detect what has been done, that's impossible. It detects things that are still on the surface. Based on the analytical technology used in that instrument, it would take appreciable amounts on the surface for it to detect something. Also, it is limited by it's internal library of substances built by PCGS.

As an analytical chemist of 28 years, I can tell you that the Sniffer is almost worthless. It is able to detect obvious things like fillers (putty) and grease, but not much beyond that. I believe the instrument is not much more than a "fear tool" designed primarily to keep people scared of submitting altered coins to PCGS.

 

This thread provides a really good example from a grading seminar I was in. The following is an opinion. No attacks on members are to be implied.

@Paul M. posted: "Tilt the coin [back and forth while you rotate it at the same time] under a strong light [75w-100w in a dark room] and look for hairlines going in roughly the same direction." When this is not done, you me, and the TPGS may miss the cleaning. "Based on this image, the problem area might be the obverse around the olive branch." Note the dark patch. This is possibly the place the light buffing "ate" too far into the coin's surface. Light cleaning that leaves the entire surface covered with parallel hairlines is the main reason that beautiful coins like this are down graded to "details" or MS-61. Or, it's possible PCGS made a mistake. It happens." Yes, the TPGS make mistakes but NOT in these situations. TPGS wish to grade coins as high as they can. "Straight" grades sell. It makes everyone happy. If they "detail" a coin, it is an extremely rare occurrence that it was a mistake. The "sniffer" is for chemical alterations, not mechanical alterations such as cleaning.

@C-B-D posted: "To me the coin's fields show no [?] luster." Actually, this coin has virtually ALL of its luster. Looks at the grainy appearance between the UNITED down to the eagle's head. Should be frosty, but there's no luster left. Sharp detail but no originality. Someone wiped it fairly harshly." Now, we are back to this: I can HARSHLY POLISH the entire original surface of a Mint State coin until the round piece of metal (our coin) has the details of an About Good AND IT WILL STILL HAVE COMPLETE LUSTER (the reflection of light from its surface); yet that luster will appear different from the original mint luster it had before it was polished. That's why buffed, cleaned, and whizzed coins are so attractive to the less informed collectors who buy them. They have luster!

 

I'd think a poorly-rinsed dip (thiourea, that is) wouldn't show visually as plainly on gold as it might silver (to warn the user), nor would it really damage the surface of a noble metal. That would show up on a sniff, wouldn't it?

Either way I'm fairly sure PCGS' reasons were the result of a visual inspection rather than a chemical one. As I mentionend, one set of images does not a diagnosis make.

 

Good to know. Thanks, @BadThad

 

No way the sniffer has the sensitivity to pickup trace thiourea. As an analytical chemist I'd have to submerge the coin in a solution to extract it and then evaporate that down to have a chance of picking it up by something like HPLC. There is a huge difference between a simple, reflectance analysis (sniffer) and a trace analysis.

 

I have heard that many TPGS employees actually smell some of the coins they grade.

Perhaps the "Sniffer" and all their claims is used as a mental deterrent rather than checking each coin. While it probably works, that "wonder machine" has probably scared off a bunch of rookie coin doctors from playing with their coins.

 

Nailed it!

 

Kind of like the arguments we get into when someone refers to "cleaning" a coin and someone else goes off on the "harshly cleaning" rant. Cleaning has acquired a different definition in coin collecting than in your Funk and Waggnals. Same for luster and mint luster.

 

Your post is very true. However, when teaching a beginner about the mint luster found on the surface of an original specimen; I have found it is best to start with the "reflective shine" (its luster) that is seen on the surface of wood, plastic, and metal. Then we can move on to what causes the mint luster on a coin and what original mint luster looks like. In that way, when a student sees a whizzed, cleaned, or polished round lump of metal (what remains of the coin) that has blazing luster; they will know it is not original mint luster.

 

Remember "cartwheel luster"

 

Something to do when I retire for the 3rd time, train PCGS dogs, as their sense of smell is about 10,000 times better than a young human and millions of times that of a older collector.