Survey of CGS vs PCGS / NGC Grades

[Sword 1,377]

I did a small survey using the data from the London Coins Website on CGS graded coins that have been previously graded by PCGS or NGC. (I simply searched for "CGS ex NGC" and "CGS ex PCGS" in the auctions results). I found 72 coins sold by LCA have been graded by CGS and also by NGC /PCGS in the past. Results are as follow:

CGS Grade Average NGC/PCGS Grade Range of NGC/ PCGS grades No. of coins in sample

93 67 67 1

92 66 66 1

91 65 65 1

90 66.5 66-67 2

85 64.8 64-67 10

82 64.3 61-66 20

80 64.2 63-66 11

78 63.6 62-65 16

75 63 63 1

70 63 62-64 4

65 55 50-58 4

50 50 50 1

The sample size of 72 coins is small and so one can't draw firm conclusions. But it does suggest a few things:

The CGS scale and the Sheldon scale do not appear to be compatible for the top grades. For example, a CGS 82 coin can correspond to 61-66 on the Sheldon scale. Or looking at this another way, MS64 can correspond to CGS 70 to CGS 85. Personally, I think CGS is better off not publishing a table comparing its grades to the Sheldon grades. If the two scales are really comparable, then CGS might as well grade using Sheldon like the other TPGs.

Alternatively, it can suggest that graders are not particularly consistent.

[TomGoodheart 378]

A CGS 91 was graded lower than a CGS80?! Something very worrying there!

Whether it's consistency or comparability, it does suggest you shouldn't make a decision about who you have your coin graded by lightly.

It could have a dramatic effect, depending on where and to whom you might eventually wish to sell.

[azda 978]

A CGS 91 was graded lower than a CGS80?! Something very worrying there!

Whether it's consistency or comparability, it does suggest you shouldn't make a decision about who you have your coin graded by lightly.

It could have a dramatic effect, depending on where and to whom you might eventually wish to sell.

I think it would depend on what was graded, at CGS91 isn't that a proof? Therefor the PCGS/NGC grade should be PF whatever. Just took a look at the CGS site and CGS91 is aFDC meaning the coin was a proof issue Edited September 20, 2015 by azda

[TomGoodheart 378]

A CGS 91 was graded lower than a CGS80?! Something very worrying there!

Whether it's consistency or comparability, it does suggest you shouldn't make a decision about who you have your coin graded by lightly.

It could have a dramatic effect, depending on where and to whom you might eventually wish to sell.

I think it would depend on what was graded, at CGS91 isn't that a proof? Therefor the PCGS/NGC grade should be PF whatever. Just took a look at the CGS site and CGS91 is aFDC meaning the coin was a proof issue

Well, I'm not much up on grading, so that could be the case. But if we drop down the table so proofs aren't a consideration, wouldn't the person with the CGS85 that graded US 64 be a bit unhappy that a GGS70 graded the same? Surely there's something odd going on there?

.

[azda 978]

When I got my 1860 halfpenny graded by CGS I checked their website for prices equivalent to specific grades. The finest known at the time was a CGS80, I didn't expect mine to come up to that grade, at the time a CGS80 was valued by them at £750 so you'd assume my apparent "finest known" graded at CGS82 would be around £800-£1000, but nope, everything went backwards, the CGS80 is now £500 and mine now at £575

[Sword 1,377]

I did a small survey using the data from the London Coins Website on CGS graded coins that have been previously graded by PCGS or NGC. (I simply searched for "CGS ex NGC" and "CGS ex PCGS" in the auctions results). I found 72 coins sold by LCA have been graded by CGS and also by NGC /PCGS in the past. Results are as follow:

CGS Grade Average NGC/PCGS Grade Range of NGC/ PCGS grades No. of coins in sample

93 67 (PF) 67 (PF) 1

92 66 (PF) 66 (PF) 1

91 65 (PF) 65 (PF) 1

90 66.5 (PF) 66-67 (PF) 2

85 64.8 64-67 10 (1 is SP65 2 is PF64)

82 64.3 61-66 20 (1 is PR65, 1 is PF61)

80 64.2 63-66 11

78 63.6 62-65 16

75 63 63 1

70 63 62-64 4

65 55 50-58 4

50 50 50 1

The sample size of 72 coins is small and so one can't draw firm conclusions. But it does suggest a few things:

The CGS scale and the Sheldon scale do not appear to be compatible for the top grades. For example, a CGS 82 coin can correspond to 61-66 on the Sheldon scale. Or looking at this another way, MS64 can correspond to CGS 70 to CGS 85. Personally, I think CGS is better off not publishing a table comparing its grades to the Sheldon grades. If the two scales are really comparable, then CGS might as well grade using Sheldon like the other TPGs.

Alternatively, it can suggest that graders are not particularly consistent.

I have added PF/PR to the higher grades.

I think the reason that the CGS valuation for the 1860 halfpenny 1*+A has went down because LCA sold an example in 2014 (UNC with a tone spot on the bust and some light deposit on the reverse, highly lustrous and very rare in this high grade) for only £240. They sold another one in 2013 CGS 75 for £100. They are only trying to make the valuation a bit more realistic. Personally, I don't pay much notice to CGS valuations. I have brought coins for one third of the CGS valuation in the past.

[Rob 3,104]

I don't lose any sleep over the valuations imposed by CGS or any other grading service. I find that a coin either appeals or it doesn't. If it appeals, the next question is whether the price is reasonable and can I afford it? At no point have I referred to the 'suggested price'. If you look at prices often enough, a list price will be superfluous after a while. Even the rarities will generate a subconscious ballpark figure, despite none having gone through auction in recent times.

[mhcoins 95]

A very interesting article ...

I have just had a former CGS coin regarded by PCGS (PARIS) and this coin never lived up to the CGS billing.

I sent in a 1893 Proof Halfcrown which was graded CGS UNC82, according to the references i had obtained this therefore should have graded elsewhere at 64/65. Unfortunately it only graded PCGS PF63 CAM. That being said its worth a lot more now its in its new holder.

[Paulus 1,954]

I have watched the PCGS video on micro-grading (or was it NGC?), but quite how they can distinguish between a 63 and a 64 is beyond me!

[PWA 1967 2,023]

The prices of cgs of which i do have a bit of an idea are in general high (as everyone knows) we determine what to pay.

However there are numerous that are IMO to low.

1934 penny in unc £50 (i have been looking for ages).

1911 Gouby X good fine £100 (scarce)

and plenty others especially the ones they have graded 85 mint state copper pennies with full lustre are scarce for any year.

Some worth more some worth a lot less i am sure i have paid sometimes more than i should of as

I might not see another as nice (scarce) for a few years so just bought it.

Having looked at grading in some detail i would say that a cgs graded coin is done a lot stricter especially with regards coins being rejected for problems.

I have numerous coins i have submitted to cgs one was NGC MS65 came back as cgs75.

Alternatively i have sent a MS 62/3 that came back as cgs 82.

I dont tell cgs they were slabbed before as the grading i feel would then not be influenced by another opinion.

That is not to say the other grading companies have a bigger audience and may return more money at auction or resale.

Pete.

[Sword 1,377]

I can understand why someone might want to send a CGS 82 to PCGS / NGC in the hope of it making MS65. No one can dispute that PCGS / NGC has a bigger audience than CGS esp. outside the UK.

What can one hope to gain by sending a PCGS / NGC MS65 to CGS (assuming it has been attributed correctly)?

[Peter 615]

Freaking hell grade what you see.

TPG are not wanted this side of the pond.

Why oh why oh why.

[PWA 1967 2,023]

I can understand why someone might want to send a CGS 82 to PCGS / NGC in the hope of it making MS65. No one can dispute that PCGS / NGC has a bigger audience than CGS esp. outside the UK.

What can one hope to gain by sending a PCGS / NGC MS65 to CGS (assuming it has been attributed correctly)?

It was just a coin with a ticket sword(out of a slab )and was sending a batch anyway.

[Sword 1,377]

I can understand why someone might want to send a CGS 82 to PCGS / NGC in the hope of it making MS65. No one can dispute that PCGS / NGC has a bigger audience than CGS esp. outside the UK.

What can one hope to gain by sending a PCGS / NGC MS65 to CGS (assuming it has been attributed correctly)?

It was just a coin with a ticket sword(out of a slab )and was sending a batch anyway.

I see.

[VickySilver 805]

Let's not forget the 1935 specimen crowns that I posted - wherein the CGS 85 was vastly inferior to a PCGS 65...

[PWA 1967 2,023]

Another one i bought already slabbed 1857 penny pcgs MS65 cgs 78

Can name numerous others just using an example uin 19251

[PWA 1967 2,023]

Let's not forget the 1935 specimen crowns that I posted - wherein the CGS 85 was vastly inferior to a PCGS 65...

Yes vicky i agree they are both independent and should be treated as so.

As per the earlier post cgs should not be comparing themselves with the sheldon scale IMO

[Sword 1,377]

Freaking hell grade what you see.

TPG are not wanted this side of the pond.

Why oh why oh why.

We all have our reasons for wanting or not wanting to get all / some / a few/ one of our coin(s) slabbed... This has been argued to the death already.

[cathrine 70]

I'm not a statistician, but I know this discussion needs to address the shape of the statistical probability vs. third party grade distribution curve for the major TPG systems. In a prior submittal to this forum, I addressed NGC vs. PCGS grades for Victorian copper and bronze. Since CGS publishes population data, I'll "try" to use that info to make some comparisons with the US graders' results.

Of course, one of the difficulties is that both PCGS & NGC use a color index (BN, RB, & RD) as well as a numerical grade, and that color index does have an effect on the grade. In the CGS system, the color also has an effect, but that effect is reflected in the grade.

This difference complicates the comparison problem. However, if we combine the each of the number of PCGS & NGC coins for all colors at every grade and compare those distributions with the CGS distribution, the results should give us a valid comparison.

I'll report on such a study after I've done the task. (the results will only apply to Victorian copper & bronze circulation coins because I'm not currently interested in the other possibilities; I leave such tasks to other interested parties).

[cathrine 70]

I've concluded the task, and I have the results. However, when I try to attach the Excel files referred below, I can't do so.

If you wants to see those files, please send me your email address.

The grading data was collected from the NGC and PCGS websites on January 21, while the CGS grading data was

taken on September 29

.

The CGS data applies to 624 coins (167 copper & 457 bronze), the NGC data applies to 1,007 coins (401 copper &

606 bronze), and the PCGS data applies to 483 coins (190 copper & 293 bronze).

The grading data is presented in the attached Excel spreadsheet ("TPG Comparison - Victoria Young Head

Halfpennies - Data"). It should be noted that for comparison purposes I have replaced the numerical grades by a set

of grading levels (1-8 for CGS and 1-6 for NGC & PCGS). Such a mechanism enables us to calculate and compare

statistical measures between data sets that use a different range of numerical grades.

Some statistical parameters for the various grading data distributions have been calculated using the EasyFit

statistical package; the results are displayed on another attached Excel spreadsheet ("TPG Comparison - Victoria

Young Head Halfpennies - Statistics").

It may be helpful to give some definitions for the statistical parameters that were calculated:

1. Mean is the average value of a data point (in grading levels).

2. Variance is a measure of how far a data point is from the mean (in grading levels). The higher the variance, the

more spread out the distribution of the data is.

3. Skewness quantifies how symmetrical the distribution is.

• A symmetrical distribution has a skewness of zero.

• An asymmetrical distribution with a long tail to the right (higher values) has a positive skew.

• An asymmetrical distribution with a long tail to the left (lower values) has a negative skew.

• The skewness is unitless.

• Any threshold or rule of thumb is arbitrary, but here is one: If the skewness is greater than 1.0 (or less than

-1.0), the skewness is substantial and the distribution is far from symmetrical.

The mean values (in grading level) for the different grading services are:

CGS - 3.479 (copper), 3.799 (bronze), & 3.713 (copper + bronze)
NGC - 3.568 (copper), 3.861 (bronze), & 3.745 (copper + bronze)
PCGS - 3.616 (copper), 3.881 (bronze), & 3.776 (copper + bronze)

All of those values lie between the third and fourth grading level, which is 78-80 for CGS and 63-64 for NGC and

PCGS. The remarkable closeness of these results would lead me to conclude that CGS 78 = NGC or PCGS 63 and

CGS 80 = NGC or PCGS 64 for copper and young head bronze Victorian halfpennies.

More conclusive evidence to support those equivalences can be found in a third attached Excel spreadsheet ("TPG

Comparison - Victoria Young Head Halfpennies - Percentiles").

What is a percentile? A percentile (or a centile) is a measure used in statistics indicating the value below which a

given percentage of observations in a group of observations fall. For example, the 20th percentile is the value (or

score) below which 20 percent of the observations may be found. The tabulated values were again calculated by

using the EasyFit statistical package.

The first table shows the grading levels corresponding to each of the percentiles, while the second table shows the

same information, except that now the grading level is given by the grading service's numerical grades.

Notice that the 50th percentile is CGS80 for all data sets and NGC64 or PCGS64 for all data sets. This is a perfect

match for the percentiles regardless of which data set is selected.

Now let's take a look at what CGS publishes on it's website about the major TPG service equivalences:

CGS90 = MS66
CGS88 = MS65 -66
CGS85 = MS65
CGS82 = MS 64 -65
CGS80 = MS 64
CGS78 = MS 63 -64
CGS75 = MS 62- 63
CGS70 = MS60-61

The percintile data shows that CGS85 = MS65, CGS82 = MS64-65, CGS80 = MS64, CGS78 = MS63, CGS75 =

MS62-63, and CGS70 = MS62. This is very strong statistical evidence that the equivalences published by CGS is

correct for copper and young head Victorian bronze halfpennies.

Quod Erat Demonstrandum!

[Paulus 1,954]

That's very good work Cathrine!!!! Maybe you should send the results of this survey to the TPGs concerned, they would be interested!

[cathrine 70]

Although I was unable to upload the Excel files referenced in my discussion, I was able to upload text versions of those files, which are attached.

TPG Comparison - Victoria Young Head Halfpennies - Data.txt

TPG Comparison - Victoria Young Head Halfpennies - Statistics.txt

TPG Comparison - Victoria Young Head Halfpennies - Percentiles.txt