£40,480.32

Astounding difference in Auction price between 2020 & 2023 for the 1 Mohur - William IV.

NGC   MS63   Apr 2020   £40,480.32 

NGC   AU58   Jan 2023    £7951.49

N#25921

Any confounding variables to justify the price difference or is it the price of war causing inflation and less money for hobbies?

I think it says more about AU58 vs. MS63 than it does about 2023 vs. 2020.  I'd come to the opposite conclusion looking at this:

NGC   PR62   Jan 2020   £7951 

NGC   AU58   Jan 2023  £7951

What format of grading is preferable or ideal?

For sake of a debate - is AU58 better than a MS70 or say MS 69.

BluHawk

What format of grading is preferable or ideal?

For sake of a debate - is AU58 better than a MS70 or say MS 69.

I don't think I understand the question.  These coins are graded on the Sheldon Grading Scale which goes from 1 to 70.  58 is well below 69 or 70.  

MS63 is a significantly higher grade than AU58. It is the number that counts on the grading scale. The difference in price in the op would suggest that 63 is a much rarer grade than 58 for the piece. 

Hibernia

MS63 is a significantly higher grade than AU58. It is the number that counts on the grading scale. The difference in price in the op would suggest that 63 is a much rarer grade than 58 for the piece. 

Thanks - this answers my query