Little black sambo book copyright 1948 last page has the letter C not sure what the letter means?

A series of letters or numbers on a copyright page is usually used to indicate the edition of the book. Many publishers will use an ascending scale (34567890 would mean the book is a 3rd edition since 1 & 2 are missing). In this case "C" would also indicate a 3rd edition since A & B are gone.