Need help with ID on a silver piece. Silver button? Silver cuff link?

[AP552]

Posting for my 10 year old son. My son and I were detecting in a our usual spot which is a old farm field that dates back to at least the mid 1800s. He dug this small silver piece, which rang up high 60s on my AT pro. I’m thinking either a broken cuff link or a button with no shank. No markings on the front. It’s slightly concave and has a 6 pointed star on the back, no writing. I included a photo of the our other finds from that day for size comparison. As always any help is appreciated.

 

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[Toecutter]

60s is low for silver,more likely to be nickel and would be why theres no markings, it does look like silver though...

 

[AP552]

I know high 60s isn’t what I normally get for silver but I’m thinking low content silver, came out clean, pretty much as you see it in the pictures. No corrosion, just tarnish.