There are no noticeable stains. The serial number is listed on the inside of the package. I purchased and used the official version, but I am selling it because I am disposing of an old Mac. Since I cannot guarantee its operation, I am selling it as "junk." Please purchase only if you have the knowledge to do so. Returns are not accepted. However, as it has a serial number, please understand that it is non-refundable and non-returnable.