Plate Blocks | Mountainside Stamps | United States, Mountainside Stamps have been dealing in fine stamps, coins, and currency for over 40 years. We have a large inventory of philately, including singles, plate blocks, coils, and booklets. Over 700 Plate Blocks from 1887 to 1941 Available. Large Stock of US Stamps. Types: Air Mail, Regulars, Ducks.