Very nice note! Congratulations. Absolute number one thing to do is get it AUTHENTICATED.
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You asked about rarity, okay, let's deal with RARITY:
Criswell uses Rarity 11 to indicate
1 to 5 "The rarity number is based upon the number of notes
now existing, rather than the quantity printed."
Cuhaj uses terms such as "scarce, rare, very rare"
I don't have Hugh's book so don't know terms or the numberic scale he uses.
Next:
Criswell plate note is similar to yours and is Series A, serial # 1382
Cuhaj does not have a plate note for this note.
New Bowers book, volume 6, does not deal with these particular issues specifically. He does recommend Austin M. Sheehen Jr's book
South Carolina Obsolete Notes and Scrip, published by Midlands Printing (2003)
Again

on your acquisition.