PCV valve Question

Thats an excellent question.
When they first appeared on the Chrysler line in the late 60s, there were,from what I recall, just 2 types; a straight one and a 90* one.I remember a certain 90* one had a metal tube around it and mighta slipped onto a matching tube crimped into the valve cover. I believe that was on a slanty.Those early ones were metal bodies.
I think by 1970, the nipples were plastic,but the bodies,as I recall, were still metal.Later ones were all-plastic.
As to calibrations, I have no idea.I imagine they were tuned in some way. Perhaps to ring seal/emissions/engine vacuum.Ive been waiting for them to make a one-size-fits-all-adjustable one for years, so I can quit messing with them.