That´s in nice shape considering how long it´s been around. I would call it a coat button judging by it´s size.
This chart might help you date it. There are 3 on here with seams like yours. A better picture of the back would help with ID.
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Good point it’s probably pewterDoes a magnet stick to the shank, if so it's iron and should date the button to 1760 to 1790 according to the chart posted above and I'm pretty sure the button is pewter A.K.A. "white metal", but you could test it for being silver, but if it's silver it belonged to a very wealthy person since they would be the only one able to afford a button made of "money"!!
Not magneticDoes a magnet stick to the shank, if so it's iron and should date the button to 1760 to 1790 according to the chart posted above and I'm pretty sure the button is pewter A.K.A. "white metal", but you could test it for being silver, but if it's silver it belonged to a very wealthy person since they would be the only one able to afford a button made of "money"!!
So that means the shank either brass or pewter, can you determine if it's brass color or the same color as the button itself?Not magnetic