I'll Lock Up
So it's really just the 30s and the 50s base model right?I'd think that it's the basic pattern of the body and sleeves that defines the style. Modifications such as different style sleeve cuffs, or different style collar, or pocket configurations, are customizations. Borrowing a style element from one model and putting it on another base model doesn't change what the base model essentially is.
Edit: plus the Levi's patterns of course.