Crankcase breather question

OK, well the odds are super high that it is a 2 stage with a check valve. There are all open and closed when the check valve comes into play; but just blowing into it back and forth only checks that, not whether it is a 2 stage.

This seems like an easy way to test these for the 2 stage operation:

• Attach it to a car with a stock type high vacuum at idle and also attach a vacuum gauge to the intake tract
  
• Put the open end of the PCV valve up by your ear (no, not INTO your ear LOL) and listen for the tone of the 'whoooshing' sound
  
• Blip the throttle hard so that the vacuum drops way down
• Listen for the 'whoosh' to increase and get louder when the vacuum drops

There are some oddities in the PCV world. One 4 banger engine I have, when stock from the factory... had nothing but a tiny restriction in a hose nipple running to the intake manifold. No check valve, nothing but that restriction.