The Silver finish is a polished Aluminum blank made from a flat 14G stock material. The stamping is a 3mm or 1/8″ number. I love the concept of GPS addresses. Where you live, where you married, met or so many personal meanings a certain spot on the planet can have. I use a heavy hammer to achieve the deep impressions, they will last longer and add a more organic look to the piece. Personal message on the back if you please. These are now available in my Etsy shop.