Perplexed by this little thing

[ClovisOak]

Read as a Quarter in the silver range, and came out sparkling with no tarnish from my back yard about 5 inches down. Seems heavy for it's size. Airfoil shape. On one of the faces is a faint circle from manufacturing is my guess. Tire weight maybe? Seems to shiny for that though... Probably something somebody has found before and knows exactly what it is.
Thanks

 

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[TxMike]

My guess is that it is a "key" that fits in a keyway to lock a gear or something onto a spline that rotates. The small circle mark is from the set screw that is tightened down against it to hold it in place.

 

[ClovisOak]

Thanks might be I see what your saying. I live near an airport so maybe from a plane? Seems to be too well made for my tractor.

 

[FoundInNC]

Looks like an adhesive style tire weight(for cars with nice rims)

 

[unclemac]

a link from an old Seiko watch