I found this button while md'ing yesterday. Wondering if it could be miletary or not. It appears to be copper or brass and the back of it has completely rusted away. It is about the size of a dime. Thanks, Joseph
The only known actual US Navy buttons with an iron back were 13-to-14-millimeters in diameter, for use on a kepi-hat's leather chinstrap. You say your ironbacked button is about the size of a dime, which is within a hair of 18mm. So, your button is most probably a civilian-clothing "Fashion button" imitation of an actual US Navy button.