So considering the overwhelming response to this topic let me throw out another idea.

The entire reason I've believed the PS return line has markings is based 100% from the reproduction hoses offered today. I have yet to be shown a single survivor return line photo with a marking to support the reproduction is not correct or correct. Very strange for this community and feeling a bit like a snipe hunt.

Is it possible that PS return lines had NO MARKING?
Questioning my own though, it makes little sense that a manufacturer would not mark hose, but who knows?!