Hard, dark residue that smells like gunpowder on the drawer slide bottoms

I picked up this 8- drawer dresser off market place, mid-century look. Not sure of which made it.

But when I pulled out the drawers and saw this stuff, I didn’t know what it is. My husband took a knife and scrapped some of it off and said it smelled like gunpowder. This now, very dry, oil/paste/wax(?) seems to have been applied intentionally on each of those slide bottoms. Have no clue what it is and I tried to do some research, but can’t find anything. Closest thing I’ve found is cigarette smoke permeating furniture – but that doesn’t quite explain the actual stuff inside. Would anyone have some knowledge on this?

Edit- also have no clue what the large splotches are on the back wall. May be the same stuff – it pooled and dried at the corner.