I remember seeing that cel with the "Dame!" 
theme song--I *think* that was an Ending.  But 
the thing is, that Ending was made up entirely 
of clips from the show, and only the Kaoru at 
the end with the umbrella was a new 
animation made especially for the Ending.  So 
the cel is both an Ending Credits cel and a 
regular production cel from one of the 
episodes (sorry, I don't know which one!).

Hope that helps.  ^_^