Edward I Newcastle Pennies, relative scarcity of Class 10?

[Coinery]

Does anyone have any insight into the relative scarcity of the three Newcastle classes, measured against themselves? 
 

Over the last 3 or 4 years I’ve managed to pick up a class 3 and a class 9 in good grades, but have struggled to find the class 10 in a similarly collectable grade, with the attached coin bearing the full Edward legend the best I’ve found to-date.

[Coinery]

The class 3 and 9 coins available in much better grades generally.

 

Edited 27 minutes ago by Coinery