What was the sole basis distinguishing Springers from Cockers prior to official breed standardization?

Answer

Size, weight, or height criteria

For an extended period, the differentiation between what became the English Springer Spaniel and the English Cocker Spaniel was purely quantitative and based on physical size, rather than fundamental differences in their job duties or conformation. The larger spaniels used for flushing were referred to as Springers, while the smaller ones performing similar duties were called Cockers. Breeders might even find a litter containing puppies that varied in size, leading to them being designated as Cocker or Springer puppies based strictly on achieving certain weight or height benchmarks as they matured.

What was the sole basis distinguishing Springers from Cockers prior to official breed standardization?
animalDogbreedlineagespaniel