Thank you for this interesting information. We are both, apparently, aware
that CMG is asserting this idea.

However, it doesn't really answer the question.

It is a "claim" in the sense that they are asserting a particular right to
control the use of Mark Twains' image (e.g. paintings or photos or visual
representations of his image).

This "claim" must have a basis in law to be enforceable in court.

So the question is, what is the legal basis of the claim?

This is not a matter of works published before or after 1923, it is an issue
of whether you may, for example and hypothetically, paint a picture of Mark
Twain as he was prior -- let's say -- to 1900 and show it to people or sell
it.  It is not a matter or reprinting works that were not first published
after the cut-off date for copyright claims.

Does anyone know, clearly, what the basis of this claim is other than that
they are claiming it?

Thank you.

Edward Summer
THE BUFFALO FILM FESTIVAL