Looks to me like someone tried to re stamp the number to alter its ID - might be they innocently enough wanted to keep their old number so tried to blur out the old number and re stamp it with a new number. Might of course be more sinister but having bought bikes / projects where numbers have been tampered with in the past I'd say appart from putting some buyers off it makes little difference as Dvla couldn't give a rats backside if you report it to them in case it might be nicked.