The quantity issued are estimates based on available information, primarily from Brookman's, "The United States Postage Stamps of the 19th Century- Volume II" and "Linn's U.S. Stamp Facts 19th Century", published by Linn's Stamp News. These numbers are simply estimates based on the best information available and are subject to revision. The design dimensions are from Luff unless otherwise noted.

Of all the issues of the 1861 Series, the 24¢ stamp may prove the most difficult to determine the exact Scott number since all stamps of the two major listings, Scott 70 and 78, are variations on the lilac and violet color themes, with the possible exception of the "steel blue" and even that stamp is thought by some to be merely a color "changeling" of the violet stamp. According to Brookman, there was only one issue of the 24¢ 1861 stamp, with all of the printings made from a single plate, PLATE 6. To be sure, the ink was modified over the years this stamp was produced, but the reasoning for a separate listing for Scott 70 and Scott 78 is somewhat muddled.

Although the Premieres Gravures, formerly Scott's 56-62, are now listed as essays in the Scott catalogue, they are included here for completeness. Note that on the 1¢, 3¢, 5¢, 10¢, 12¢ and 90¢ stamps there are small design differences. On the 24¢ and 30¢ stamps there is no design difference, the only way to distinguish these from the ordinary issued stamp is by color. Fortunately the red orange of the 30¢ and the black violet of the 24¢ are very distinctive, making these trial colors relatively easy to distinguish from the regularly issued stamps.

Special Printings: The following information applies to all of the 1861 re-issues. The Special Printings were issued to showcase a complete set of the U.S. issues for the first World's Fair officially held in the U.S., at the Centennial International Exposition of 1876 in Philadelphia and also to provide stamps for collectors and others to satisfy numerous requests. Reissued stamps were valid for postage. The 1861 reissues can be distinguished from the ordinary issue by their extremely white paper, absolutely white gum and very deep clear color (Brookman). 

Quantity issued: Estimates are based on available information primarily from Brookman, "The United States Postage Stamps of the 19th Century- Volume I", "Linn's U.S. Stamp Facts 19th Century", published by Linn's Stamp News. These numbers are simply estimates based on the best information available and are subject to revision. Please report any updates or corrections via email.

Bibliography and suggested additional reading:

Basic Information: 
The Postage Stamps of the 19th Century, Volume 2, by Lester Brookman (1966)
The 2009 Scott U.S. Specialized Stamp Catalogue (Amos Press 2008)
The United States 1¢ Franklin 1861-1867, by Don L. Evans (1997)
The Harry F. Allen Collection of Black Jacks - A Study of the Stamp and Its Use, by Maryette B. Lane (1969)
The PAID Markings on the 3¢ U.S.  Stamp 1861, by George W. Linn (1955)
United States Letter Rates to Foreign Destinations 1847 to GPU-UPU, by Charles J. Starnes
History of Letter Post Communication between the United States and Europe, by George E. Hargest
The U.S. Issue of 1869 Preceded by Some Additional Notes on "The Premieres Gravures of 1861", by S. Ashbrook (1943-44)

Design dimensions: 
The Postage Stamps of the United States, John Luff  (1902 and 1937)

Colors:
The Encyclopedia of the Colors of United States Postage Stamps - Volume 1 Issues of 1847-1868, by Roy H. White (1981)

Websites of interest to the 1861 collector: 
 The Collectors Club Philatelist at www.collectorsclub.org.
 The Chronicle of the U.S. Classic Postal Issues at www.uspcs.org
Siegel Powersearch at Robert A. Siegel Auction Galleries, Inc.