The Vintage Postcard featuring Bear Dens in the Zoological Park in Detroit, Michigan is a Linen Postcard from the era of 1930-1945. Made of paper, this Original postcard measures a standard size of 5.5 x 3.5 inches. It is a collectible piece that captures a snapshot of wildlife in a zoo during that time period, making it a unique and charming addition to any postcard collection.