Washington Head: Denomination in Numerals: 1¢: Imperforate

US408 - Flat Plate Imperforate
US 408 Flat Plate
US531 - Offset Imperforate
US 531 Offset

Printing Method and Watermark Check – You must first determine if the imperforate stamp was printed using the flat plate or offset method;  the 1¢ rotary press imperforate stamp was not issued. If the stamp is offset, it does not have a watermark. If it is flat plate, you must check for the presence of a watermark. 

Printing Method Watermark US Number Privately
Perforated by the Following Companies/Types
Flat Plate Single-line 408 Brinkerhoff I, II, IIa,
IIb; Farwell 4A, 4B, 4A5, 5A4; International Vending Machine; 
Mailometer I, IV;  Schermack III; USAV I, II, III
Flat Plate none 481   Schermack III only
Offset none 531 Schermack III only

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