"tktoolkit" is the label used at [SourceForge] to identify [Tk] as a project.  
[D. Richard Hipp] also maintains a sort of mirror
[http://cvs.hwaci.com/tktoolkit/] with SF snapshots, as a [CVSTrac] demonstration.
The demonstration's "timeline" [http://cvs.hwaci.com/tktoolkit/timeline] thus 
constitutes a convenient view on core Tk check-ins.