The last ones I bought from Peter DeBella appear to be more cosmetic than functional, unless I'm missing something. When held up to the light, it is possible to see through it (and suck or blow both directions). The Debella part has Willys part # WO-A6895 and Ford part # FM-GPW6769 on the box and AC1543018 and ORDN A-336400 stamped into the body of the PCV valve.
I have also got a couple of (NOS from e-Bay) AC PCV valves that are labelled as CV476 or 5647235. They appear identical except that the AC476 valves are silver instead of black and the internal plunger isn't through drilled so they do seem to be more or less a one way valve.