How to Identify US Stamps: Complete Guide by Era

The United States has issued postage stamps since 1847, producing thousands of distinct varieties that range from common definitives worth a few cents to rarities valued at over a million dollars. Identifying a US stamp accurately requires examining its design, perforation gauge, paper type, watermark, and printing method. This guide walks you through every major era of US philately and the specific markers that distinguish each period.

US Stamp History at a Glance

US stamp production breaks into several well-defined periods, each with distinctive printing techniques and design conventions. Understanding which era your stamp belongs to is the first and most important step in identification.

• 1847–1869 — Early Classics (imperforate, then first perforated issues, grills)
• 1870–1893 — Bank Note Era (multiple private printers, secret marks)
• 1894–1938 — Bureau Issues (government-printed, watermarked paper, flat and rotary press)
• 1938–present — Modern Era (Presidential series, commemoratives, self-adhesives)

Early Classics (1847–1869)

The first US stamps were issued on July 1, 1847: a 5-cent Benjamin Franklin (Scott #1) and a 10-cent George Washington (Scott #2). These stamps were imperforate—printed in sheets and cut apart with scissors or a knife—so their margins are irregular.

Key identification features

• No perforations (1847–1856): All stamps before 1857 are imperforate. If your stamp has clean-cut straight edges on all four sides and features Franklin or Washington, it may be from the 1847 issue.
• First perforated issues (1857–1861): Perforation 15 was introduced. The same designs as the imperforate issues were reissued with perforations, creating entirely different Scott numbers (e.g., Scott #18 vs. Scott #1).
• 1861–1869 designs: New designs during the Civil War era feature Franklin (1c), Jackson (2c), Washington (3c), Lincoln (15c), and others. Look for the distinctive "grill" pattern embossed into stamps from 1867–1869—small waffle-like impressions pressed into the paper to prevent stamp reuse by making the paper absorb cancellation ink more thoroughly.
• Paper: Thin to medium, usually bluish or grayish tint. Some 1847 issues appear on slightly brownish paper.

Understanding grills

Grills are small embossed patterns pressed into the paper to help ink absorb and prevent stamp reuse. They were used primarily on the 1867–1869 issues. Grills appear as a rectangular area of tiny raised or indented bumps. An essential identification detail is the orientation of the grill points: earlier grills have points up (pushed into the paper from the back, so points face upward on the front), while later grills have points down (pressed from the front, points visible on the back). This orientation helps distinguish grill types and detect forgeries. Grill varieties include:

• A Grill: Covering the entire stamp. Extremely rare.
• B Grill: 18×15mm. Scarce.
• C Grill: 13×16mm.
• D Grill: 12×14mm.
• E Grill: 11×13mm. Most common early grill.
• F Grill: 9×13mm. Most common overall.
• Z Grill: 11×14mm. Extremely rare—the 1-cent Z Grill (Scott #85A) is one of the most valuable US stamps.

1869 Pictorial Issue

The 1869 Pictorial Issue (Scott #112–#122) marked a dramatic departure from US stamp design. For the first time, stamps featured subjects beyond presidential portraits: a locomotive (#114), a shield and eagle (#116), the SS Adriatic steamship (#117), the landing of Columbus (#118–#119), the signing of the Declaration of Independence (#120), and a shield with flags (#121). These bi-color stamps were printed in two passes, which occasionally resulted in the center vignette being printed upside down. The resulting inverts—Scott #119b (15c), #120b (24c), and #121b (30c)—are among the most prized US stamp errors, with values ranging from tens of thousands to over a million dollars.

Bank Note Era (1870–1893)

From 1870 to 1893, three private companies held contracts to print US stamps: National Bank Note Company (1870–1873), Continental Bank Note Company (1873–1879), and American Bank Note Company (1879–1893). The designs are nearly identical across all three printers, making identification a genuine challenge.

Distinguishing the three printers

• National Bank Note (1870–1873): Printed on hard white paper. No secret marks. The earliest 1870 printings carried over the grill from the preceding era (Scott #134–#144 with grills; #145–#155 without grills).
• Continental Bank Note (1873–1879): Introduced "secret marks"—small design additions to help distinguish their printings. For example, the 1-cent Franklin received a small curved line in the ball of the numeral "1"; the 2-cent Jackson shows a small dash under the tip of the left ribbon.
• American Bank Note (1879–1893): Printed on softer, more porous paper that absorbs ink differently. Colors tend to appear slightly duller. Same secret marks as Continental, but the paper is the key differentiator.

1893 Columbian Exposition Issue

The 1893 Columbian Exposition stamps (Scott #230–#245) were the first US commemorative stamps, issued to mark the World’s Columbian Exposition in Chicago. The series featured 16 values from 1 cent to $5, each depicting a scene from the life of Columbus. The high-value stamps—especially the $4 Isabella (Scott #244) and the $5 Columbus (Scott #245)—were expensive even at face value and remain highly sought after. A mint $5 Columbian can catalog for several thousand dollars.

Bureau Issues (1894–1938)

In 1894 the Bureau of Engraving and Printing (BEP) took over US stamp production. This era introduced watermarked paper and eventually rotary press printing, both of which are critical identification markers.

Watermark identification

Bureau Issues used two main watermark types, visible when a stamp is placed face-down in watermark fluid:

• USPS single-line watermark (1895–1910): Letters "USPS" in a single line, spaced across the sheet. Each stamp shows only a portion of a letter or sometimes no visible watermark at all.
• USPS double-line watermark (1910–1916): "USPS" in double-line block letters. Easier to detect than single-line.
• Unwatermarked (1916 onward): After 1916, watermarked paper was discontinued. If your Bureau Issue stamp shows no watermark, it dates to 1916 or later.

Flat press vs. rotary press

Starting in 1919, the BEP began using rotary presses alongside flat-bed presses. Rotary press stamps are slightly taller or wider than flat press stamps because the curved printing plate stretches the design:

• Flat press stamps: Measure approximately 19–19.5mm × 22–22.5mm for standard-size definitives.
• Rotary press stamps: Measure approximately 19.5–20mm × 22.5–23mm. The difference of roughly 0.5mm is detectable with a good ruler or perforation gauge.

Washington-Franklin Issues (1908–1922)

The Washington-Franklin series is one of the most complex areas of US philately. Although the stamps share only two basic portrait designs—George Washington and Benjamin Franklin—the series comprises hundreds of distinct varieties. Collectors must examine multiple identification markers simultaneously: single-line vs. double-line watermark (or no watermark), flat press vs. rotary press printing, perforation gauge (perf 12, 11, 10, or 8½), and subtle design types (Types I through VII for some denominations). A seemingly ordinary 2-cent Washington can range from a few cents to thousands of dollars depending on these characteristics. The Scott US Specialized catalog devotes many pages to this series alone.

Coil stamps

The US began issuing coil stamps in 1908 for use in vending machines and affixing machines. Coil stamps are perforated on two sides only—either top and bottom (for horizontal coils) or left and right (for vertical coils)—with straight edges on the other two sides. Identifying genuine coils is a particular challenge because trimmed sheet stamps can mimic the straight-edge appearance. Key markers include: paste-up pairs (where one coil strip was spliced to the next), line pairs (showing a colored guide line between two stamps from the flat-plate printing process), and slight size differences on rotary press coils. Expertization is strongly recommended for valuable early coil issues.

Modern US Stamps (1938–Present)

Presidential Series (1938)

The 1938 Presidential Series (Scott #803–#834) featured every US president from Washington through Coolidge, with denominations from ½c to $5. These are common but form an attractive set for beginners.

Liberty Series (1954) and Prominent Americans (1965)

The Liberty Series introduced larger-format definitives, while the Prominent Americans series shifted to notable figures beyond presidents. Both are readily available in used condition.

Commemoratives and special issues

Since the 1940s, the USPS has issued dozens of commemorative stamps each year. Key identification points include:

• Size: Commemoratives are typically larger than definitives.
• Denomination placement: Modern commemoratives show the denomination prominently, often with "USA" and "FOREVER" (from 2007 onward).
• Self-adhesive vs. lick-and-stick: After 1992, most US stamps transitioned to self-adhesive backing. Water-activated stamps became uncommon after 2000.

Perforation Gauges for US Stamps

Perforation gauge—the number of perforation holes in a 2cm span—is one of the most important tools for US stamp identification. Common US gauges include:

• Perf 15: First US perforated issues (1857–1861).
• Perf 12: Standard for most Bank Note and early Bureau issues.
• Perf 11: Common on Bureau Issues from 1908 onward.
• Perf 10: Used on some rotary press coils and sheet stamps (1920s).
• Perf 11×10.5 or 10.5×11: Compound perforations found on certain Bureau Issues. Measuring both horizontal and vertical gauges separately can reveal scarce varieties.

Scott Catalog Numbering Basics

The Scott catalog is the standard reference for US stamps. Numbers are assigned chronologically, with letter prefixes for special categories:

• No prefix: Regular postage stamps (Scott #1 through the thousands).
• C: Airmail stamps (C1–C150).
• E: Special delivery.
• J: Postage due.
• O: Official stamps.
• Q: Parcel post.

When buying or selling, always reference the Scott number to avoid ambiguity. A "1-cent Franklin" could be dozens of different stamps; "Scott #300" is exactly one.

US Stamp Errors & Varieties Worth Money

Printing errors and scarce varieties can make otherwise common stamps extraordinarily valuable. The most famous US errors and varieties include:

Quick-Reference: US Stamps by Era

Tips for Beginners Examining US Stamps