Off-hand I don't know about any *complete* sets of proofs for any Twain
novels, but certainly fragments of proofs from various stories and essays
survive. Quite a few have appeared at auction over the years. Never mind
setting copy for TS, FTE, etc. I think proof sheets for PW survive, and that
they reveal fewer marginal drawings than the final book edition. I have
proof sheets for HOW TO TELL A STORY and a later edition of LIFE ON THE
MISSISSIPPI . Some of the early states of the canvassing copies of his works
were made up using pages printed from proofs --the sample copies of RI are
one very good example, and there are others.  I have Twain's copy of
SKETCHES, not a proof, in which Twain did not simply revise the text for his
lecture readings, but actually restored some text edited out of the
published version --changing the printed text about an editor whom he called
a "crawling insect" who was "braying" back into the "jack-ass" as Twain
first portrayed him, etc. The polar opposite of what you'd see in a proof,
but it makes you yearn for those proofs to see what else might have been
toned down, and by whom. More important, it should serve to make modern
editors extremely cautious in how they accept or interpret Twain's apparent
use of language even in his "original" published texts.

While it's not a novel (although some might argue the point on other
listservs),  the proof sheets for WALDEN survive (at Huntington) and that
would seem to undercut MB's claim somewhat.

Kevin Mac Donnell
Austin TX