Need help with an old flat button I found today

[ptango]

Managed to pull this beauty out of the local park amongst modern clad. MY FIRST FLAT BUTTON! WOO-HOO! However I dont know anything about it. There are no markings on the front and the back only has a concentric ring of arrows with a broken shank. It measures 3/4" and read like a deep penny. Any help would be greatly appreciated. Thanks. Also found a Sterling silver pendant and $3 in clad. Not a bad day.