Difference between Crown and Sovereign?
A: Good old Internet...google and wikipedia

Difference between Crown X#7b and Crown X#P17?
A: Believe X#P17 is piedfort. More research is required. Weight, thinkness, edge (smooth or reeded), ...
Difference between Crown (Gold X#7c) and Sovereign (Gold X#8)?
A: Don't have an answer yet. More research is required.
Difference between Crown (Silver X#7b, Silver X#P17) and Sovereign (Silver X#8a)?
A: So far, weight appears to be the big differentiator between the three (X#7b = "regular", X#P17 = piedfort, X#8a = 4.4199g). More research is required.
This topic welcomes any CCF members with information to share as not much is known (at least I'm still learning)
