HyperCard 2.x 

Hold down Option as you select "About Hypercard...".

In 2.1, you get a dialog describing your system setup.  In either 2.0 or 2.1, the chooser name, if you've entered one, appears in the "HyperCard by" title.  (That is, if you entered "Joe Cool" as your name in the Chooser (6.0) or Sharing Setup (7.0), the top of the window will read "HyperCard by Joe Cool".  If you have no Chooser name, one of the names of the many developers is put there.) Also, on any recent Mac (ones that require System 7.0.1 or 7.1), you will be told your system is a "Macintosh Macintosh". 

(Thanks to Seth Theriault for more info.)