It is news, and false news too, it seems to me.  Yes, SLC played a guitar every
 now and again, but he prefered a piano. I don't know that he ever played
guitar on stage (though his twin on the Twins  of Genius tour in 1884 did, to
accompany himself on some creole tunes).  Is it possible that such an artifact
escaped notice of the Twain community in general for so many decades? Sure, if
a private collector never put the thing up for sale. But before anyone believes
 the contents of any advertisement to be true, some fact checking is in order.
What proof is there of the instrument's provenance?  Are there any photos of
the Clemenses in which a guitar is visible, and is it possible to identify the
make & model from them? I have my doubts, but Marianne Curling at the Mark
Twain House in Hartford would be the best expert on the matter.  Marianne, are
you out there?  What do you say about this guitar?
                                                      Andy Hoffman