Converting Sheldon Scale Grades to a One Hundred Point Grading Scale
Since my last blog, I spent a great deal of time pondering how to go about converting the Sheldon Scale (SS) to a 100 point scale that I now call the Metric Grading Scale (MGS). This was not easy to do due to the idiosyncratic ranges of grades for categories of coin grades. Sheldon essentially has four basic grade categories; Good, Fine (and all the kinds of fine a coin can be), Almost Uncirculated and Mint State).
This nicely allows us to work in quartiles with MGS. Good coins range 1 to 25. Fine coins range from 26 to 50. Almost Uncirculated coins range from 51 to 75 and Mint state coins range from 76 to 100.
SS grades do not follow any logical progression in grade score because 10 points are allotted for Good coins. Fine coins have 39 points allotted. 10 points are allotted for Uncirculated coins and 11 points are allotted for mint state coins.
To derive at the MGS score, use 25 as a numerator and divide by the SS coin total number of points assigned to that grade.
For good coins, 25/10= 2.5. Then add 2.5 for each step in the grade. A good SS 1 becomes a good 2.5 MGS. a SS 5 becomes MGS12.5 and an SS 10 would be MGS 25.
In SS there are 39 points for all of the types of Fine coins (F, VF, XF). Significantly more points in this area of the SS compared to the other categories. In fact almost four times the number of points assigned to any other category. LOL, serious voodoo here!
The equation for this grading quartile is 25/39= .64 To arrive at scores for MGS in this range begin with 26 as that is the first number in MGS for this grading category. For each point in A F 12 becomes a 28.3 because 26 is the first grade in this quartile. F12 gets two points added to 26 to become 27 + 1.28 for 2x .64. In MGS this becomes a F 28.6 (rounded off following math rules of course).
Lets look at an XF 45 from the SS: Here your formerly Sheldon XF coin becomes an MGS 66.8 which is an AU grade in MGS. Because in the SS the allocation of points is so large that some of your coins when you convert the score will actually be low grade AU coins in MGS.
Almost Uncirculated coins follows the same formula as for Good coins: 25/10= 2.5 for each grade step. An example for an MS 58 MGS grade would be
2.5x9 = 22.5. Add that to The SS grade and this coin is an MGS 80.5
Mint State coins have a slightly different formula as there are 11 points allocated on the SS. For mint state coins 25/11= 2.27 An MS 60 under SS becomes 78.27 for example and an MS 70 SS becomes a MGS 94.8 (using the rounding rule for math).
With this system, your coins will not be downgraded, but there is a significant potential for your coins to be graded higher with the advent of the use of artificial intelligence in grading coins. I will write about the use of A.I. in my next Blog.
Comments
Kepi
Level 6
Great ideas... but math was not my strong subject! haha I am open to change and new ideas. Looking forward to hearing more about this. It is concerning the possible extra costs of having all of our more valuable coins re-slabbed for this conversion. Good luck with this venture! ; )
Long Beard
Level 5
I like you thinking. As I've always believed, change is inevitable. The how, why and when become the challenge. However, third party graders (especially the big three- PCGS, NGC and CAC) will fight it tooth and nail. But in the end, it's more often human nature to resist and fear change. So yes, I'm a proponent of change.
AC Coin$🌎
Level 6
Bama, your proposal would be just fantastic. However, traditionals rather go for short numbered stems when appraisingor evaluating. It would be great to see a 100 scale realistic value within all standards known. But we know somehow something oddly commercial is behind numbering. Great blog, take care. AC
Rebelfire76
Level 4
That’s a lot of math conversion. Though your 100 point scale makes logical sense. It will be the redefinition of grades that will throw most for a loop. Like why isn’t a MS 70 a MGS 100? Obviously there would be things to be worked out in the conversion, but in the realm of grading, I’m waiting to read more about he AI which may make grading more consistent.
I. R. Bama
Level 5
Sheldon would have been much better off with a 40 point scale.
I. R. Bama
Level 5
Good question. An SS MS 70 only converts to a 94.8 on the MGS because of the severe flaws in the SS. An MS70 can not be lower than a 94.8 but conceivably could be graded higher up to 100. Remember, the conversion only fixes a SS coin to the corresponding MGS grade. Because there are 30 more points in MGS, SS coins could be regraded higher, but never lower than the converted grade on the MGS.
It's Mokie
Level 6
I think you should flesh it out a bit more, add some information on the transition process and submit it to the Numismatist for publication. This little group of lost souls should not be your target audience. (:
I. R. Bama
Level 5
I agree and thanks for the encouragement. Next blog will be about the AI and what I have learned about efforts to do just this!
It's Mokie
Level 6
I wonder if the value of the millions of currently slabbed coins would suffer initially. I would suspect so. I think this would be a boon to the big 2 (or3) grading services as people scramble to get their more valuable coins reslabbed asap. a very very expensive proposition for the hobbyist and even for the dealers. I like your idea but I think it is unfeasible in our lifetime.
I. R. Bama
Level 5
I thought about this and came to the conclusion that if people wanted coins regraded, they would just as easily have a higher valued con, but certainly no one should be losing money on this. One can choose to convert the SS to MGS or not. But the real value in this will be when AI uses this system to grade coins. Imagine owning your own software that grades your coin more accurately. My vision puts the technology into the hands of each collector as I would like to see it available for all to use individually as opposed to paying TPGS for each coin.
Longstrider
Level 6
WOW! My head hurts. I need to read this over a couple of times. Seems like you have it down.? More reading on my part is needed. I'll be back. Thanks.
I. R. Bama
Level 5
I think I got all the math right, but as with any academic project, revisions may be necessary, but I am excited to have something that will allow for easy conversions from SS to MGS