Trying to Clear Pre-1923 Artwork for Film

Dear Rich: I work in the film industry and often experience frustration and confusion around the use of art work supposedly in the public domain. When I am trying to clear a piece of pre-1923 work (let's say published in the U.S. for practical purposes) I am often told that the rule is 70 years after the death of the artist (or sometimes 100 years). Many works published before 1923 have authors and illustrators that died significantly later. Does the "work for hire" or commissioned work by a corporate entity rule come into play here? In other words, because the piece was commissioned (or written by an employee) does that make the creator's copyright subject to the pre-1923 law? Any work first published in the U.S. before 1923 is in the public domain regardless of the lifespan of the author or authors, and regardless whether it was made by an employee or contractor under work for hire principles. Only works published after 1977, or unpublished works, (or unpublished works that were later published) are contingent upon author lifespans. When in doubt, check this handy public domain chart, or download a copy of Steve Fishman's excellent public domain book.