BGS and CSG grading algorithms may Share similarities
 

I was trying to figure out how subgrades determine a card’s final grade.

A web search led me here:

https://codegolf.stackexchange.com/q...gs-final-grade

Scrolling down the the Answers section, a user, Charcoal links to an interactive page where you can test the sudgrades of your BGS slabs, but it also sort of works on CSG subgrades as well, for the most part.

I tested it on three CSG slabs. Two matched, but the third didn’t until I rearranged the order of values to get the grades to match. It seems that if the code accurately models BGS and CSGs algorithms, one of my cards may have been overgraded by a half point.

I believe the code was based on observational data from BGS subgrades and final grades, but I’m not a coder nor do I fully get the math of grading.

A question I have if anyone can answer, is why do the order of values matter in determining the final grade as they do in the webpage?


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The four subgrades are corners, edges, surface, and centering. I think you're asking why they're not equally valued in the overall grade. It's likely because some are more important to eye appeal, based on the grading company preference based on what they think customers prefer.

When people first look at cards at arm's length, they immediately notice the centering and corners. Edges and surface (light creases, etc) are less noticeable. At high grades (like above 7), the overall grade can only be like 0.5 grade higher than the lowest subgrade.

As you move down the grading scale, you can get a grade 1-2 points higher than the lowest subgrade. It's not a straight average, because a card with a pinhole (surface of 1) could still have Gem Mint 9.5 centering, corners, and edges. But the card will likely max out at a 2.

Andy Broome, a head grader at CSG came from BGS. So it would make sense that they share similarities.