From the scan it appears as a genuine offset transfer error.
Although this type of error would be easy to duplicate using a computer printer, the diagnostic on this note is the cross-hatch pattern of the transferred image.
This type of error occurs when a sheet is misfed into the press and the plate comes in contact with the cloth surface the sheet rests on. The plate image is transferred to the cloth image which is then picked up on the backside of the next sheet to be printed. The crosshatch pattern is caused by the weave of the cloth.
Computer fakers are not able to duplicate the weave.