Hi Fabian,
I see two (or more) possible alternatives for solving this.
Assuming that the box only receives one type of entity you can:
1. Create a state variable (for example st_CurrentBoxType) and every time an entity enters the combiner you assign the entity type to this state variable. This way, one the box is completed and exits the combiner you will be able to assign it the st_CurrentBoxType.
2. The other way is to execute a search step once the box is full. You can use "ModelEntity.BatchMembers.FirstItem" as match condition to locate the first batched entity, then in the found branch use an assing step to assign the ProdType from the found entity
I'm sure there are a lot of ways of doing that... hope this helps
saludos