There is only one file type that uses the .MCX extension:
MICRO CADAM-X/6000 Model Data File
3D model format used by Mastercam X and X2 CAD/CAM software; used for developing 3D models of parts, molds, and fixtures; may contain solids, surfaces, and wireframe data; commonly referred to the MC-X format.
MCX files are also supported by CATIA-CADAM software.
Updated: April 28, 2007