Thanks for the correction, I didn't spot that at all. I know that Australian immigration match passports at both ends of trips - I'm dual-national and if I don

Thanks for the correction, I didn't spot that at all. I know that Australian immigration match passports at both ends of trips - I'm dual-national and if I don't get the right passport at the desk they ask me for the other one. So I would suspect this is domestic and the stamp is a vanity thing.