Ok, maybe idiot terminology was incorrect. The curved mark in question is raised with squared edges. What I was thinking was, there was something on the planchet before the strike. Given that it's only on the background and not the letters.
"Die deterioration/wear is not considered to be an error at all unless it involves terminal failure of the die. Die chips, cracks, and deterioration doubling are an acceptable part of the minting process and are not screened out by the Mint. Most of the coins minted by a die pair during their life will be of the late die state variety and will show some degree of these issues. Once the die deteriorates to the point of involving majors breaks such as a cud, that is when you have an error as that is considered to be a terminal state close to die failure. A die will be taken out of service if a cud or major break is noticed because the next step would be a shattered die(a valuable and rare error)." biokemist6 04/28/2012