Pressure Regulating Valve - How to Test??

hi and hello:

anybody know how to test the "gold colored" Pressure Regulating Valve (PRV) on the bench? Its installed in a 1968 Dodge Dart 270/SL-6. How about testing in the car? I know the switch connector (black in connector with a terminal connection on the top) provides the "ground connection" thru the dash brake light. How do I know the PRV is correctly working and the internal piston is correctly centered??

Thx guys. I am attempting to bleed the brakes to insure brakes are properly working Thought I would understand if the PRV is functioning. It looks like the original so install a new one??

Thx....A Body Forum is the best.