Create one-to-many to two fields in different table
I would examine your model and see if it needs some normalization.

It would appear that the two types of model are sub-types of a common model.  I have found this kind of implementation requires some design.  Using the same id sequencing for both tables opens up a number of options for implementation.  

Creating an intermediate Model table containing the Model id, modelTypeID, and any common fields contained in the subtypes also helps.  Depending on the query requirements you may be able omit either the subtype tables or the model table from some queries. 

If there are few columns in the sub-type tables (EffModel and BkgModel) you may want to add them as nullable columns in the Model table.  Alternatively, you can implement the normalized model and use a UNION query, or outer joins to both subtype tables.

In any case you will need to ensure the integrity of the data and ensure the records created match the ModelType.