I assume this is different for custom entities in the systems, there is a possibility to get different ObjectTypeCode if you created the entites seperately on each system instead of using import/export, there is also a chance that if your systems are not
exactly the same from the start (f.e. if someone at some time created an entity on your prod system but nothing was created on the test system) that the OTCs are different (f.e. if the number is already in use when importing).
To the best of my knowledge the OTCs should stay the same during export import unless they are already in use on the system you are importing to.
Halldór Jóhannsson