If you enlarge the video and freeze-frame certain images you can see that
his vest seems to fold over from the left and button from the right, so the
film negative does not appear to have been flipped. I've seen Twain with his
robe or coat (unbuttoned or without buttons) folded over opposite the usual
custom, but his shirts and vests are solid clues in this regard. Many
right-handed people use their south paw to drink. With tea, perhaps this
makes even more sense, leaving the right hand to stir with a spoon. At any
rate Twain was right-handed, a topic that I think has been kicked around in
this forum before, and the fact confirmed I think by a passage in one of his
letters mentioning an injury to his right arm that hampered his writing,
etc.

On the other hand (sorry), Twain smoked both right and left-handed, but only
one cigar at a time, of course.

Kevin Mac Donnell
Austin TX