I am thinking a scratch as well. If it was a struck through, I was going to ask if it is safe to use acetone on a proof coin to get rid of all that debris before putting it in a 2x2. Oh,by the way,great job on the pics. It is not easy getting good pics of a proof coin John1
( I'm no pro, it's just my humble opinion ) Searched 6.5 +/- Million Cents Since 1971
im not sure about strike through, but id think its hard to get a staple to make a big scratch like that and perfectly follow through the letters without a gap inbetween where the staple would ineveitably "skip" on the surface when it hit the raised lettering. I may be wrong but thats my input.