Well, it can't be a gun case because it has no lock, it's the wrong shape to hold a dart board, what are the dimensions? It is sitting on a table, and looks to be maybe 2' tall? It could be a key cupboard. Look to see if there are any holes where there were once hooks.
Unfortunately, whatever it is, I doubt it is antique. Not only do I see no signs of age or wear, but the knobs are and hinges are attached with modern mass-produced Phillips-head screws.
The hinges also appear to be modern. I wish I had better news for you!