There is a key difference.
In photoshop, reset your image to the original file each time you press print and "enhance" again. See how consistent your results are making the prints look identical.
If you click "save" you have created a new "negative".
Okay, I can’t state this with absolute certainty, but I’d bet that in the past 70 a new, more economical and more easily printed negative has been made. Exactly when, I cannot say.