Welcome to Coin Talk. Since you posted this on the error coins forum, You must think there's an error on your quarter. The photo of the obverse is too blurry to see anything. What kind of error do you see? Other than that, it looks like a normal 1978 Clad Quarter. It's made of an outer layer of copper-nickel (.750 copper, 250 nickel) bonded to a core of pure copper. Diameter 24.3 mm. Weight 5.67 grams with a tolerance of +/- 0.227 grams (5.443-5.897) Info taken from RedBook. EDIT. If you're referring to the color, IMO it's a result of environmental toning.
If you're intent on looking for Mint errors, it would help if you knew what a normal coin should look like.
