Model : B-4 , Format : 3 1/4 x 5 1/2 , Film size : 122 , One of the most popular sizes and styles of folding camera ever introduced was the "postcard" . An early accessory for the camera was an interchangeable plate-back which permitted ground-glass focusing and the use of holders for dry plates. Original List Price : $78.00us ,c1908-1909.