I'd like to mention that my first step was to contact the seller politely, state my concerns about the unit in a very non-confrontational way, and ask for a refund MINUS shipping charges and $10 for his trouble. I was turned down.
The problems with the calculator are:
(1) Burn/melted spot on the plastic case (not the overlay, which could easily be replaced).
(2) Two missing feet.
(3) The inside of the battery compartment is badly corroded. One battery terminal is nothing but a large solder-blob which was apparently put there after the terminal corroded almost completely away.
This guy is not a regular calculator seller, I do not believe. It's possible he's entirely justified in his own mind, but I believe that anyone should be willing to make a refund in this situation. He's not.