The manual fill valve is basically a large brass fill valve on the side of your tank with a separate, much smaller bleeder valve above and to the right of it that when opened emits propane to tell you when the tank is full.  The Auto-stop valve has a fitting for the fill hose to hook up to, an internal auto-stop valve behind the fitting, and there is a tube from the the tank(above and to the right) to the fill valve that propane comes from when the tank is full that triggers the auto-stop function.

Mark in AK

----- Original Message -----
From: Preston Grimes <87westy@GMAIL.COM>
Date: Wednesday, August 2, 2006 12:23 pm
Subject: propane valve -- manual or autostop?
To: vanagon@GERRY.VANAGON.COM

> How can I tell which of these is on my tank?
>