This website lists all selectors, known to the editor, for use by programmers of the Gestalt Manager on the Apple Macintosh computer. It is no longer maintained and for reference only.
Major versions were released about every two months and were widely distributed. Regular updates (every 1 - 2 weeks) were distributed through the mailing list which is no longer active.
The first ever published 'Undocumented Gestalt Selector Codes' can be viewed here too.
The GSL is no longer maintained and submitted information is no longer processed.
The latest version of Jean-Pierre Curcio's GestLab application is available for download from his website. It was the recommended Gestalt selector hunter's tool and saved config files were accepted as contributions to the GSL.
In 1994 Apple announced to abandon the gestaltMachineType ('mach') selector. Henry Norr wrote about the implications and context in MacWEEK.