Kraft Cheese Slices - here is an advertisement from 1955, showing five different types in their packages:
And in this one from 1956, just the Swiss Cheese Slices:
For me, a real grilled cheese sandwich means cheddar - but I wouldn't turn it down if you made one for me with the 2% American - shown here in 2007:
And , also from 2007 - individually wrapped slices:
Here's the "Now" (as in - in my fridge right now). This is what I really want:
Give me what I want, what I really really want......