Did the mesh or louvre grilles on a Mack LT indicate engine type?

[Jamaican Bulldog]

I notice some Mack LT or LTL have louvre type grilles and some have mesh style. Did that indicate engine type or were those options no matter the engines or year of build?

[mrsmackpaul]

I think louvers were the earlier ones and mesh the later one's, only a complete guess though 

 

I also think that mesh grills had louvers in behind the mesh so maybe the ,esh was just a option to protect the louvers 

 

Paul