We don't have synonyms for mattoir yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are mattoid.
(n) :
(engraving) A kind of coarse punch with a rasp-like face, used for making a rough surface on etching ground, or on the naked copper, the effect after biting being very similar to stippled lines.
(n) :
(engraving) A kind of coarse punch with a rasp-like face, used for making a rough surface on etching ground, or on the naked copper, the effect after biting being very similar to stippled lines.