No scholarly credentials here, but have a good ear for style, and
that ain't Twain.  It has none of the literary richness,  or sly
surprise, that is inevitable with Twain.  Like John surmises, it's a
much more recent construction, but I don't even think it was an
attempt to imitate Twain.    Just my take, fwiw. We have some
quotation experts on the list, so I'm sure it will be clarified, and
if I'm wrong, I couldn't be in better company than John's!

Ben

Benjamin N. Wise, Ph.D.
Professor Emeritus
Keene State College