McClary Royal Charm Coal and Wood Stove

[Hughton]

I have been using my McCLary Wood stove for many seasons at a summer cottage and it is working well. I never really looked at it too closely before now and am curious to know the function of the box attached at the back behind the fire box and beside the flu. Does anyone know if there a reason or a way to open it up for cleaning?
Here is a photo of the front and back of the stove.

 

[EatenByLimestone]

Is it open on top or bottom? It might be heat shielding. If closed up completely, it might hold an asbestos panel.