I'm no expert on this subject, but I may be able to supply a partial answer
to Jerry's original question about “Samuel Clemens” vs. “Mark Twain.”

After TOM SAWYER fell into the public domain in 1932, many American
publishers began issuing unauthorized editions of the book. The novel was no
longer protected by copyright, but the name "Mark Twain" was trademarked.
Consequently, unauthorized publishers generally--if not always--published
TOM SAWYER under the name "Samuel Clemens." Heritage Press must have
published its first edition under that name, too. When or why they shifted
to "Mark Twain" I do not know. Heritage and its affiliated publisher,
Limited Editions Club (which issued pricier numbered copies of the same
books with the illustrators' signatures), kept the books in print for many
years. If I'm not mistaken, the books themselves don’t always indicate the
years in which they were printed. I'm wondering if Heritage got permission
from Harper's (MT's authorized publisher) or from the Mark Twain Company to
use the name “Mark Twain.”

At some point, other unauthorized publishers also started issuing books
under the name Mark Twain. I'm not sure when that began. It may have been
the late 1940s, as I've noticed that the Grosset & Dunlap edition
illustrated by Donald McKay was published under both "Clemens" and "Mark
Twain." I haven't seen a Grosset edition with "Clemens" as author, but a
"Mark Twain" edition I have in hand right now shows a 1946 copyright for
"special contents" (presumably the new illustrations). My copy also shows
copyright notices for the Mark Twain Company. This makes me wonder if
Grosset decided that having "Mark Twain" on the cover was worth the extra
cost of whatever it had to pay the estate for permission. If anyone reading
this note can add further details, I would welcome them.

An amusing sidelight about the confusion over "Samuel Clemens" vs. "Mark
Twain" can often be seen on eBay. Occasionally, eBay dealers list
unauthorized editions of TOM SAWYER and claim they're rare because they have
the name "Clemens" on them. Such editions typically list no publication or
copyright dates at all. In those books, the only date that remains is
"1876," the date Mark Twain placed at the end of his Preface. I've seen more
than one eBay auction describe one of those books as a first edition
published in 1876. The dealers typically remark that the browned pages of
the books are indications of the books’ great age. This is ironic, as the
pages of true first editions are likely to be less brown than those of the
1930s editions, which were mostly printed on cheap, high-acid newsprint.

Jerry also mentions an edition of TOM SAWYER illustrated by  Thomas Hart
Benton, who illustrated the Heritage/Limited Editions Club edition of LIFE
ON THE MISSISSIPPI. I’ve never seen a TOM SAWYER illustrated by Benton, but
abe.com lists several expensive copies of a Limited Editions Club edition
that meets that description. Hart also illustrated HUCKLEBERRY FINN; 1994
Easton Press reprints of that edition can apparently be obtained for modest
prices.

On another matter, Jerry suggests that Norman Rockwell was the only artist
to depict the whitewashed fence accurately. I’m not sure this is correct.
Aside from the fact that Rockwell’s illustration doesn’t match the book’s
description of a fence nine feet high and thirty yards long (of course,
Henry Sweets has argued that those dimensions existed only in Tom’s
imagination), other illustrators (including Donald McKay) have depicted the
fence with vertical boards.

Jerry also asked about the book that contained an illustration that Livy
Clemens ordered removed. That was the picture of Mark Twain in flames in
LIFE ON THE MISSISSIPPI.