I contemplated 'messing' with the background but then decided I liked how the scratches on the coin appear to have sort 'spread' on to the black background, does that make any sense?
The weirdest bit about this shot is that that is a black piece of card as the background! To the naked eye there is no dust, no marks just black...under the macro lens these white (?) dust like marks appear!
This one is right on the money! Great use of negative space and tack sharp. Almost too sharp -- be nice to reshoot this one with a shiny new coin and a black background free of dust! Nice job.