Retained strike through error - staple in a half dollar

[Twitch]

I found this error last night and haven't been able to locate much information on it. I believe it's a staple that's been struck through and retained on the reverse of a very nice bicentennial Hal dollar. Posted some pics in the CRH forum but would like to get opinions on rarity, preservation method, cause, value, etc. I know virtually nothing about errors. Any information is appreciated. I think it's awesome that the letters and stars on the back are stamped right into the staple.

Thanks,

 

[cudamark]

Pretty cool!

 

[dejapooh]

Very nice find. Rare. Likely over $100.