There were several brands back in the day that were happy to advertise on the writing on the back "Stainless steel back", which means that the rest of the watch ain't stainless steel. Was this a cheap attempt to mislead people into thinking that the watch was all stainless?

 

No. They were actually boasting about the back being steel, as opposed to chrome (typically). It was a point of pride (i.e. "We may be cheap, but not that cheap!")

Obviously that seems a bit silly now, given how clear it is that steel was/is a superior metal for watch cases. And of course the better brands used full steel cases on most, if not all of their watches.