You may want to contact the Smithsonian (ask for the curator/person in
charge of the vast permanent exhibition of printing presses at the Museum of
American History) or the Newseum in Virginia. It probably wouldn't hurt to
contact Tom Muzzio, the current publisher of the Virginia City Enterprise.
He's proud of his paper's Twain connections and may be able to answer some of
I do know, however, that Mergenthaler's linotype didn't come into use
until 1884 or so, utterly eclipsing the competing typesetter a fellow named
Paige was trying to perfect, with considerable financial backing from Clemens.
Hope this helps! Good luck!