Tried 3 times to contact Eric (on vacation maybe?)

The valve at top of his pressure tester...should it

 

be leak proof or not leak proof?

 

and turning screw on tester only depresses the valve stem (to allow pressure in)  on what ever you are testing?

Correct. The little thumb screw just depress the valve for flow. The main collar nut is what makes the seal.

Thank you.

 Guess I 'll  keep in plastic bag  for now on.  As the botom of my tool box certainly won't rust