This is one of the best books for identifying any series of stamps. So many adaptations to stamp production in a relatively short time period led to many varieties of what looks like the same stamp to the untrained eye.
Scott #450 2¢ Carmine Type III Printing Method: Rotary press Subject: George Washington Number issued: 292,184,500 Perforations: Perf 10 horizontally Watermark: Single Line USPS wmk Issued: December 21st, 1915 Value Used: $7 - $12 No postmark with gum (MH): $30 - $50 Full perfect gum (MNH): $50 - $80
I don’t have this stamp just yet 😁 Scott #: 350 4¢ orange brown Subject: George Washington Printing Method: Flat Plate Perforations: Imperforate Watermark: double line USPS (see below) Quantity Issued: 283,000 Issued: August 15th, 1910 Value Used: $200 - $250 No postmark (MH): $150 - $200 Full perfect gum (MNH): $350 - $500