How do you test old style pcv ?

You boys are sure making me feel old. Here is the tool for measuring the effectiveness of your PVC. On a running engine pull off the breather on the v/cover opposite the PVC. Lay device over the hole. If there is adequate vacuum in the crankcase the check ball will be pulled into the safe zone.View attachment 1715797011
Just did an internet search, none for sale, sometimes on eBay.