I've seen wiring devices manufactured in Mexico (Leviton) stamped with the NOM/ANCE seal (Normas Oficiales Mexicanas, or Official Mexican Standards).
ANCE stands for Asociaci√≥n Nacional de Normalizaci√≥n y Certificaci√≥n del Sector El√©ctrico (National Association for Electrical Sector Normalisation and Certification).
Ditto electrical appliances made for sale in Canada/USA/Mexico, they're stamped with C-UL-US, CSA (sometimes) and NOM/ANCE.
I belive ANCE may also be in charge of wiring standards.
See here: http://europe2.dynamicweb.dk/Default.asp?ID=85
and here: http://www.ance.org.mx/