Belt Clip Not Included

A few weeks ago, I broke the "indestructible" Otterbox that contains my work cell. phone.  Actually, I broke the holder which holds on my belt, not the box itself.  (My boss has broken three, but in a different manner than I.)  The company offers a replacement warranty, although it took until I returned from my training trip before the new one arrived.  In the meantime, I've been carrying the phone-in-a-box in my pocket.

They sent an entire new box and belt clip in the package, even though all I need is the belt clip.  What am I to do with the new box?  Should I keep it, in case I need it?  Should I sell it to someone who wants it for less than the price of a new one?  Would it be ethical to sell it, or does it belong to the company?  (This is a gray area.  Obviously, the company bought the first one for me, but since the replacement was free, and since it wasn't requested or needed, does the company own the replacement?)

I've already thought of the marketing slogan:  Perfect for purses or capacious pockets.  (Wouldn't Capacious Maw be a good name for a rock band?)