What is this?

This really isn't an engine problem but it is in the engine bay so I figured I would put it here. I had something in that same area on my Duster which is now just two empty holes and I can not remember what was there. I don't know if it was the same thing that is in the pic since I have two holes and this to me would look like it would have one with that black part removed. So I am just trying to remember what could have been there, my Duster is a 73 and it had emissions equipment on it when I got it. I'll take a pic of the holes I am talking about in my car tomorrow and add it to this thread.

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