NonDirectional or CombinedDirectional Specular lightmaps rendering mode.
Note: this property is only serialized when building the player. In all the other cases it's the responsibility of the Unity lightmapping system (or a custom script that brings external lightmapping data) to set it when the scene loads or playmode is entered.
You can continue reading here if you want to know what the different lightmap modes do.
Did you find this page useful? Please give it a rating: