Thanks for the response, Frank, but I'm still confused after looking at the two Mann filters, and a Fram. The Fram I had for another VW looks like it has nothing- you can see straight down to the bottom- no springs or anything.

The Mann W719/5, which I'm remembering I may have bought for my Mexican air-cooled Beetle, has the spring just about an inch under the threaded end-you can't see to the bottom, or even the side. 

The W719/12, which Van-Cafe says is the one they sell for the Vanagon, has a spring on the bottom, but ci can't see holes and a rubber seal. 
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Ed, yes,very easy.  When your looking at the bottom of the filter you will see
holes around the perimeter just inside the rubber seal.  Beneath those
holes is a rubber flap.  No flap, no anti-drain back valve.  The
spring loaded valve you see inside the filter is the over pressure valve.
All filters have them.

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