View-Master is the trademark name of a line of special-format stereoscopes and corresponding View-Master 'reels', which are thin cardboard disks containing seven stereoscopic 3-D pairs of small color photographs on film. The View-Master system was introduced in 1939, four years after the advent of Kodachrome color film made the use of small high-quality photographic color images practical. Tourist attraction and travel views predominated in View-Master's early lists of available reels, most of which were meant to be interesting to users of all ages. Most current View-Master reels are intended for children. In 1911, Sawyer's Photo Services began operations. In 1918, brothers Fred and Ed Mayer bought part of Sawyer's. In 1926, Harold Graves joined Sawyer's and was responsible for Sawyer's producing photographic postcards and album sets as souvenirs. Later, photographic greeting-cards were added to the product line and sold to major department stores.