Free US Shipping on a Rare 2011 Grand Rapids Michigan National Button Society Convention Button on Card. I believe the material is plastic but I can't tell for sure. I don't know if the button is vintage or if it was made for the convention. The button has not been cleaned or touched in any way. It measures about 1 and 5/16" in diameter and is etched NBS2011 on the back. The button is from an estate collection. Thank you for your interest and please message me any questions you may hav