I had the Marshall Brass regulator untill a couple of years ago when it became unreliable. (it went from 11 inchec WC to 8 inches) Marshall Brass went out of business and the regulator was no longer available. I replaced it with a Camco that froze up once and whistled a lot. You could not see the red window with the plastic tank cover in place. I recently found out that Marshall Excelsior now makes an exact duplicate with an added test port to measure pressure. I bought and installed it last month and am pleased with it. I can now see the red window from the flip open cover on my tanks. Here is where I bought mine:
MEGR-253