Ah, what a perfect drawing of a very interesting subject. At first, one gets a feeling that is actually looking at photo. Artist has a great talent for capturing things and is talented in shading and other drawing techniques which make this drawing so realistic.
Lines are perfect, nice, smooth and realistic. If this is referenced from a photo then I'm sure the goal is achieved. I really like the textures on this drawing, it's practically so real that it's almost a photo.
Shadings are godlike, I have never seen such consistent and perfect shadings in quite some time. I would lie to ask what tools did you use? Is it only pencil or you used other techniques like charcoal or ink?
Background is also perfect, I won't say anything more on it.
All in all this is one of the best drawings on dA and you are very talented artist that deserves more recognition.