There are two "scores," and in the "normal" sets they are pretty easy to figure in Excel, or I guess on paper if you want to. If you have all the coins in the set, your Set Rating is the same as your Weighted GPA. The more you are missing from the set, the lower the Set Rating, so if you have only one coin from an entire set but it's MS70, your Set Rating would be very low, but your Weighted GPA would be 70 - the highest. In the lowball sets, it's scored as "in inverse order. For example, PO-1 = 70 and MS/PR-70 = 1" which sounds pretty simply but I can't for the life of me figure the formula for Set Rating. In my hypothetical set I have a 2000P, 2000D, and 2000S, which PCGS has assigned a "weight" based upon rarity of 1, 2, and 3 respectively. If my coins are: 2000P - MS65 2000D - MS65 2000S - MS60 Then my Set Rating and Weighted GPA is 62.5, or my total weights / the PCGS assigned total weights, or ((1*65)+(2*65)+(3*60)) / 6, or 375 / 6, or 62.5 I got dinged more for the S mint being a lower grade than I would either the P or D. In my low ball set my coins are: 2000P - XF40 2000D - AU50 2000S - AU55 Then the math gets a little more complicated to figure the total weight of each coin: (71*PCGS weight) - (PCGS weight - my coins grade) so the 2000P is (71*1)-(1*40)=31 the 2000D is (71*2)-(2*50)=42 the 2000S is (71*3)-(3*55)=48 giving me a total weight of 121 So my Weighted GPA is: 71 - (my total weight / PCGS assigned total weight) or 71 - (121/6) or 50.833. However, my Set Rating is... not that. Somehow if you look here you can see that the Weighted GPA can be around 65 but the Set Rating can vary from around 2 to 25. How the #$%$ are they figuring that? Thanks for reading.
