Update June 18, 2005: Beware of Picasso, Chagall, Miro, or Matisse heliogravure prints. Heliogravures are photographic reproductions of works of art regardless of who the artists are or how famous they are; they are NOT original prints. The overwhelming majority of heliogravures that you see for sale have been cut out of books and magazines, or have been removed from portfolios. Once again, heliogravures are NOT original works of art, they are NOT original lithographs; they are reproduction illustrations and they were RARELY hand-signed by the artists whose art they reproduce.

http://www.artbusiness.com/sigwarn.html