weird structure definition in header file

["Robert P. J. Day" <rpjday@mindspring.com>]

  i'm looking at some legacy code and, in a header file, i find the
following (paraphrased for brevity):

typedef struct {
	... stuff ...
} Widgets ;

extern Widgets Widget ;


  huh?  i can see why a header file would want to define a structure
but i'm confused why the *header* file would then refer to an external
object of that type.  that's a new one on me -- typically, i'd expect
a *source* file to define such a thing and other *source* files to
contain the "extern" declaration.

  is this some subtle programming cleverness of which i am unaware?
thanks.

rday