Broke little broach or button?

[Klclark3]

I found this weird shaped thing at my colonial site, small, has a little ditch on the underside, middle might be sealed or a hole.

 

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[ohiowhiteguy]

button would be my guess..
HH..
OWG..

 

[doublet2a]

Is there threads on the outside?? Looks almost like a slot for a screw driver in the second pic.

Tim

 

[Klclark3]

No sides are smooth and sloped, middle is dirt or mud, but not sure didn't wanr to push out. Divet only on one side