Watermark Check: This stamp must be checked for watermark. Note that these stamps are seldom faked, rather they are the starting point for many of the more dangerous forgeries in U.S. philately.
Watermark | Number | Privately Perforated by: |
Double-line | 344 | Attleboro; Brinkerhoff I, II, IIa, IIb; International Vending Machine; Mailometer I, II, III, IV Schermack I, II, III; USAV I, II, III |
Single-line | 384 | Brinkerhoff II, IIa, IIb; Farwell 1, 2A3, 2B3, 3A2, 3B4, 4A3, 4B3, 4A, 4B, 4A5 Mailometer I, II, IV; Schermack II, III; USAV I, II, III |