9 times out of ten, a retread company will not find 4 of the same casings.......therefore each tyre has the same tread pattern but different brand names etc on the sidewalls. Whilst this is not ALWAYS accurate it is most of the time.
If they are retreads you will see markings on the sidewalla stating a speed limit for those tyres (normally 140kmph) I belive those markings are required by law.
From what you have said, it seems to me you have good tyres not retreads.