Each core box used different cores from run to run... There were no dedicated cores for each box, they made the cores and assembled them in whatever box was available to be built...
That's why each core has its own identity number... So they can track what cores make the parts if there are any problems...
The cores are just hard compressed sand that they have to break out of the blocks after they are molded... They are literally disintegrated after each run...
New cores are made with new sand for each run from each core cavity... The sand is put into the core cavity and a liquid is added to help the sand stick together before they compress it to make each sand core to use in the core boxes..