WTH is this that just fell out of my /6?!

I'll be a son-of-a-gun! I also found one of those on my garage floor after moving my Duster around. Also a '72 Duster, it had a /6.
Is your charcoal canister hooked up? Has it ever been monkeyed with?

This thing showed up on my floor after I had been working with the old fuel lines. I made a not-so "swag" (scientific wild *** guess) that this thing is a check valve that is in the line that runs from the charcoal canister back to the fuel tank. The '72 FSM shows it in a diagram and makes mention of it, but doesn't really show one up close and personal.
My not-so swag...
C