I (someone else) would recommend against the use of the term "facing." While there are many regional term variants, I've never heard or read of this one. It would be perhaps better to refer readers to the following terms (where they will be able to find a lot of information):
 * engraving - using small chisels (gravers) to carve line art into metal.
 * chasing - using small blunt rods to drive particularly shaped grooves into sheetmetal.
 * repoussé (embossing) - using chasing tools and a pitch bowl to shape sheetmetal into bas-relief artwork from the backside of the metal.