On the one hand, it just looks like a key fob--maybe the PO thought it was a real collector's item.
On the other hand, the way the tires project, it reminds me of the "keys" that are sometimes used to open marine water or fuel inlets. So look around your trailer and see if there are any screw-caps that have a slot with a round hole at each end--that keyfob may be the tool for opening that cap.
Key fob, you can buy them at the Jackson Center Airstream Factory store or at most any Airstream dealership.
__________________
MICHAEL
Do you know what a learning experience is? A learning experience is one of those things that says "You know that thing that you just did? Don't do that."
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