Essays are designs for stamp vignettes, stamp borders, or both combined, that were never approved and used in the final printing of a stamp. Even though a design is finally adopted with only slight modifications, it is still an "essay". To attain the status of a proof, a proposed design, or essay, must be exactly like the issued stamp for which it was submitted.
All U.S. stamps were made by private bank note companies from 1847 to 1894. Essays and printing bids were submitted by those firms. As early as 1851, the U.S. Post Office Department established a policy of advertising for stamp proposals to be accompanied by essays, or examples of the stamps to be furnished. After the bids were opened, an Expert Committee was asked to rule on the designs, colors and paper.
Today, the procedure is usually for the Citizens' Stamp Advisory Committee to pass on a U.S. stamp subject, choose an artist or artists to design a stamp for the printing medium selected, then take the final artwork to the postmaster general for his approval.
Not always is the first assigned artist able to render a satisfactory design. A case in point would be the 1984 Louisiana World Exposition stamp. On this occasion, the first artist submitted designs that were not acceptable. The Postal Service and CSAC turned to designer Chuck Ripper, who came up with the final stamp art on his first attempt.
Essays on older U.S. issues were made in small quantities; usually the outside printing firm kept several copies. Today, design essays are kept by the U.S. Postal Service; few, if any, ever reach the stamp trade in any format.
Early essays could take the form of vignette models mounted on a card. Around the design, the artist might draw in pencil cross-hatching, or even the suggested frame and lettering. Combinations of essays for the vignette and the frame were sometimes built into full models in the exact size of the final stamp.
Occasionally, essays are now prepared as artists' sketches. In a number of early cases, however, finished plate essays fully gummed, perforated, and sometimes grilled would be submitted. All such material, whether just an art sketch or final plate proof, remains an essay until the production and release of a stamp exactly like it. Then it becomes a proof.
It should be noted that reprints of stamps previously issued and sold by the Postal Service are not classified as proofs, even though such reprints may have been sold for collectors' benefit only.
When an essay was fully approved, one engraver may have done the vignette only and had proofs of his work pulled at any point. Another engraver, completing the frame and lettering, may also have had progress proofs of his work made. Two groups of proofs of one stamp were ultimately created: one for the vignette and one for the frame.
When Ripper's art for the Louisiana Expo issue was accepted, it became an "artist's proof." As engravers have copies of their work printed, these are called "progressive proofs", or "engraver's proofs." Proofs taken from a die are "die proofs"; those pulled from a plate before printing are "plate proofs." Various colors often are used in making proofs; these are "trial color proofs," but genuine design proofs nonetheless. When a proof is printed in the exact color of the stamp, it is termed a "color proof".
Although proofs are known to exist in many varied styles, those listed below are the most common:
Large die proofs were printed on paper about the size of the engraver's die block, 40 millimeters by 50mm, or larger. Margins often show the imprint, letters and numbers of the original contract printers. In the United States these large die proofs usually were printed on India paper and mounted on cards. Those with the engraver's name or an official approval designation are highly valued.
Small die proofs have extremely narrow margins, seldom larger than 3mm to 5mm in width. Approximately 300 types were printed for 85 album sets prepared by the Bureau of Engraving and Printing in 1904. These are found on a fibrous, white wove paper. Another special printing of 413 different small die proofs was made for the 1915 Panama-Pacific Exposition. These were produced on a soft, yellowish wove paper, and are extremely scarce.
Plate proofs are found on both India paper and card stock. They were made from finished plates and are excellent impressions, showing a sharpness and color far superior to the stamps themselves.
Hybrid proofs are really plate proofs of all issues prior to 1894. They have been cut to shape and pressed onto large cards to resemble the large die proofs.
Card proofs are printed on high-quality, clear white card stock, which can vary in thickness.
India paper proofs are on a thin, soft, opaque paper, which wrinkles when wet. This paper also varies in thickness and shows particles of bamboo. Strangely, India paper was developed in China in the 18th century, and was once referred to as "China paper".
The U.S. Essay-Proof Society, which has since disbanded, defined a proof as "any impression, the design of which was approved for use on an issued stamp of an established government or private post, from any die, plate, stone or type, printed for the purpose of (1) examination or reference, (2) for determination of satisfactory quality of design, color, ink, or imprinted surface, or (3) for determination of the effect of cancellation or method of separation".
The Scott Specialized Catalogue of U.S. Stamps lists hundreds of varieties of proofs and trial color proofs from the postmasters' provisionals of New York (1845) and Providence (1846) to the 6¢ 50th Anniversary of Powered Flight airmail of May 1953. The Scott roster includes only those proofs outside of government ownership.
Up until a half century ago or more, stamp proofs were available to the stamp trade. In early days, congressmen could secure them for their constituents upon request. Thousands were distributed in this manner, creating a collecting irony of sorts: The proofs of modern U.S. stamps usually are not available, while older proofs are frequently offered for sale.
Today, proofs are retained only by the Bureau of Engraving and Printing and the United States Postal Service. Engravers were allowed to keep a proof for themselves long after they became unavailable for congressional requests, but those were the only copies outside of government ownership. Occasionally, a retired engraver's estate may include a proof for outside sale, but that is extremely infrequent. The last 1953 airmail proof may have come from that source.
For all practical purposes, modern U.S. proofs are now akin to a dead country that no longer issues stamps. They are no longer obtainable by anyone.