I have one of the flour sacks (framed) and I also have a cigar box label
(certified as authentic),  It says "Copyright Wolf Bros. & Co."  It shows a
middle-aged Twain in the center with pictures of Huck (fishing) and Tom
(whitewashing a fence) on either side.  The slogan is "Known To Everyone  -
 Liked By All."

In real life, I teach copyright law and trademark law at Pepperdine
University School of Law.  Based on that, I am sure that (1) Twain was not
the first celebrity whose name and likeness were used to sell products and
(2) that Twain neither authorized nor received any money from such products.
 The privacy right that gives you a right to control the commercial use of
your name and likeness is relatively recent, and has only become widespread
in the last 30-40 years.   There, thay may be more than anyone wanted to
know.  I'm new to the list, but I enjoy it every day.