3¢ Washington Head
Flat Plate
Imperforate
Type I Flat Plate
Double-line Watermarked
Type I Flat Plate
Unwatermarked
Type II Flat Plate
Unwatermarked
Watermark and Type Check - The flat plate stamp must be checked for watermark. If it is double-line watermarked there is no need to check for anything else, the stamp is Number 345. If it is unwatermarked, it can be either of two types, type I or type II. Note that unlike the 1¢ and 2¢ stamps the 3¢ flat plate imperforate is not found on single-line watermarked paper. Many of these stamps were privately perforated.
| Watermark | Type | Number | Privately Perforated by: |
| double-line | I | 345 | Brinkerhoff I, II, IIa, IIb; International Vending Machine Mailometer I, II, III, IV; Schermack I, II, III; USAV I, II, III |
| none | I | 483 | Mailometer IV; Schermack III |
| none | II | 484 | Schermack III only |
see also Private Perforations - Vending and Affixing Machine Perforations
