This is a 19th century Scottish burr root  snuff box. This snuff box  is carved from burr root wood from a huge old tree, and has a a hinged lid, which depicts a penwork commemorative portrait of Robert the Bruce.
It measures approx 9cm w x  6cm d x 4cm h.
Burrs  occur on many trees, most commonly at the junction of the trunk with the ground or root.  
They are caused by a number of small shoots which are unable to break out, and form an interwoven, contorted but unusually stable mass. They can be very ornamental.