Inside Macintosh: QuickDraw GX Environment and Utilities / Chapter 6 - Message Manager / Message Manager ReferenceConstants and Data Types
Message Manager Gestalt Selector The Gestalt selector 'mess' can be used to determine which version, if any, of the Message Manager is installed. enum { gestaltMessageMgrVersion = 'mess' };
'mess'
enum { gestaltMessageMgrVersion = 'mess' };