WEIRD Antique TinType case photograph maybe post mortem sister and alive brother

Unusual cased Antique Tintype of a brother and sister. At first glace I thought it was a post mortem of the sister looking at her arm. Her arm is limp. Almost without bone. SUPER weird and creepy! Her expression is blank. The brother is obviously moving, so there's no question that he is alive. I am unsure that this is a post mortem tintype, so please judge for yourself. None the less, the little girls rubber arm is really unusual!

3 1/2 x 3 inches

please examine photos for condition.

Missing the other half od the case.

Email me if you have any questions.