farm house hunt

I dug this POLICE button near a tree line between an old farm house and RR tracks. It's nearly the exact size of a quarter and appears to be copper. The back is intact but rough condition and needs some cleaning overall.. Are there any button experts that know the approximate year such buttons...

Got permission to hunt at an old farm house, but only 4 hours, hopefully I can get back in for another hunt later. I found 46 coins with the Garrett AT Gold using the NEL Hunter Coil (love that coil). here is the highlights. 1918 Mercury Dime 1932 Canada one cent 1926 Wheatie 1925 Germany 10...