There is only one file type that uses the .MC2 extension:
MasterCook 5 Cookbook File
File created by MasterCook version 5 and 6, a program used for creating and organizing recipes; contains cookbook data, such as recipes, ingredients, and food preparation information; used to save the current state of a cookbook.
Cookbooks for MasterCook version 2, 3, and 4 use the .MCF extension.
Updated: March 4, 2010